| Please note the following:
| "Hey, you wanna see my pencil?
My name is Jeffy, see? It says it on my shirt, Jeffy.
— Jeffy’s first words, Mario The Babysitter!
— One of Jeffy's verbal tics.
|"ARE YOU FUCKING HIGH?!"|
— Jeffy when he is angry.
|"I HATE GREEN BEANS, DADDY!"|
— Jeffy whenever Mario tries to make him eat green beans.
|"I don't have to."|
— Jeffy being sassy.
|"Gimme see it!"|
— Jeffy asking for something.
|"Umm... Someone pooped my pants."|
— Jeffy when he doesn't want to admit that he pooped his pants.
He was originally the son of Nancy and Jacques Pierre François, but since Jacques Pierre François died and Nancy went to jail in Jeffy's Parents!, he is now currently the adoptive son of Mario and his wife, Rosalina.
Jeffy was born in a porta-potty at 7 Jeffy Street Paris, France, on August 21, 2004, to prostitute Nancy and painter Jacques Pierre François. They are both from different locations and of French descent, except Jacques, who is entirely of French descent. Nancy is also of Irish and German descent.
At some point in his life, Jeffy moved to California with his parents and Feebee, his little sister, was later killed in a bike accident as their mother took her helmet to use as an ashtray, forcing Jeffy to always wear it.
Jeffy was then dropped off at Mario and Bowser's apartment since his mother was tired of his antics. Jeffy lived with Mario and his family in the apartment (causing havoc around the house, especially towards Mario) before being evicted from the apartment and having to relocate to the new house.
After his wealthy father committed suicide and willed his money to Jeffy, Nancy returned to reclaim Jeffy in order to receive Jacques' money. After being arrested for child abuse, prostitution, and much more, she still hunts for Jeffy in prison. Mario chose to officially adopt Jeffy as his son. Jeffy then resumed living with Mario and continued to cause much trouble around the house.
Jeffy is somewhat different than the average teen, with a tall posture. He wears a blue bicycle helmet (with black messy hair under it), usually has a pencil shoved up his nose, has blue crossed eyes, along with a yellow T-shirt that reads "Jeffy".
He wears short dark blue jeans with a diaper outside of it, which he occasionally spanks. According to Jeffy, the diaper is on the outside of his pants so the diaper doesn't get dirty. Jeffy wears black Adidas sneakers. His biological appearance seems to be his blue eyes inherited from his mother, and his dark brown hair inherited from his father. His face is oval shaped with two teeth and a round nose, along with two eyelashes and a unibrow.
Jeffy's personality has gone through more changes than any other character. He started off as a mentally-challenged kid before evolving into a slightly ditzy person who swears like a sailor, explodes in anger at any slight against him, and knows a lot about perverted acts for someone his age.
He has a habit of spanking his diaper placed outside of his pants. When he is called a "bad boy", he tends to have a breakdown by throwing his head onto any surface, but calms down when he is called a "good boy" (but this doesn't happen after the episode Jeffy Loses His Pencil!). He often says "Why?" whenever someone tells him what to do or what not to do. He even keeps saying it whenever someone answers him.
However, he could have even more of a breakdown, by using curse words and being rude towards Mario and Rosalina. He likes to put his "pee-pee" in various objects, especially Cheerios boxes. He is also afraid of the most ridiculous things such as animals, toilets, snow, ostriches, a flu shot, and the number 7. Based on characteristics, it is suggested that he is on the autism spectrum. His mother delivered him to Mario because she did not love him for unknown reasons (according to Jeffy).
Not much is known about his relationship between Junior and Joseph, despite the fact that they both called him "awesome" after once surviving a game of "Russian Roulette." Rosalina is more loving and caring towards Jeffy to the point where she acts like a motherly figure and calling Mario off whenever he gets angry at Jeffy. However, Jeffy has been shown to act smart, but in a dumb way at times, such as in Jeffy's Homework! when he reasoned that the equation 8-4=8, since they are taking 4 out of the equation, even going on a profanity-laced rant.
Later, in Jeffy's Bedtime!, he called I-Am-Sam, the tall character in Green Eggs and Ham, a liar since he claimed that he liked the green eggs and ham, but the illustration clearly shows that he didn't eat the ham at all, and, despite suffering from mental retardation, Jeffy is an extremely skilled painter, the result of his late father being a famous painter. According to him, he used to live on 7 Jeffy Street before being dropped off at Mario's door. Jeffy tends to soil his pants often.
Sometimes, Jeffy can be even more demanding than Junior, as seen in Jeffy's Bedtime!, where he demands that Mario and Rosalina make him green eggs and ham, in "Jeffy Gets Potty Trained!" when he demands that Rosalina give him marshmallows instead of peas, in "The Hitman!", where he wanted Jello after Mario gave him green beans, he refused to eat his McDonalds Chicken Nuggets because he wasn't given 20 toys and threw them away, in "Locked Out", where he demanded for chocolate cake, cried when Mario didn't give him it, and locked Mario out to enjoy the cake, especially in front of Mario, and in "Jeffy Gets Help", when Jeffy yells, screams, and throws a temper tantrum because Mario said that he would not watch SpongeBob SqaurePants.
He also flips his desk in "First Day Of School!" because the teacher assigned a 10-page essay that was due the next day and cusses (mostly the F-word) at Jackie Chu, saying "ARE YOU FUCKING HIGH?!". Sometimes Jeffy seems to have a prankster personality as in "Jeffy's Cellphone!", where he prank calls several places, including an employee named Josh and a prostitute, and in "Shrek The Babysitter!", where he locks Shrek in the bathroom with the help of Bowser Junior.
During both of these videos, he seems to be less unintelligent, causing many fans to think that this could be a normal version of Jeffy, despite all of his intelligent moments in the series. Some people [who?] think Jeffy pretends to be retarded. When his real mother Nancy tried to claim him back, Jeffy begged Mario to let him stay and promised to be a good boy (and kept his promise by not playing the cat piano when he went back inside), indicating that he loves Mario very much. Jeffy's obsession with swearing may be from his mother and the way she acted in front of him and treated him.
Fortunately, Jeffy has his fair share of good deeds that battle the one ones such as being considerate to Hansel in three episodes. He is most likely misunderstood after suffering pain from his biological mother and witnessing his twin sister's death which might explain his outburst problems.
- "ARE YOU FUCKING HIGH?!?!"
- "What doing?"
- "You said Jeffy's a bad boy!"
- "I don't even know."
- "I HATE GREEN BEANS DADDY!"
- "Why you do that?"
- "The new SML store is now open, so go check it out at SML Merch.com!"
- "My name is Jeffy, see? It says it on my shirt, Jeffy."
- "HOW HIGH ARE YOU!?!"
Likes and Dislikes
- Beating Up Bullies
- Pooping in his pants
- Marshmallows on pancakes
- Playing his Cat Piano
- Annoying Mario
- Cheerios Box (love interest)
- Jacques Pierre François (most likely)
- Prank calls
- Pokemon Cards
- Fortnite (His favorite video game)
- Magic Tricks
- Board Games
- Spanking his diaper
- Nintendo Switch
- Saying the word "faggot" (in Jeffy's Bad Word!)
- Making a grunt noise
- The Bunny Do song
- Throwing stuff
- Jumping (on beds, trampolines, etc.)
- Kicking everyone out of the house
- Board games
- Chocolate cake
- Raping various things (mostly some Cheerios)
- His Pooperman shirt
- Black tar heroin
- Fidget Spinners
- Indiana Jones
- Pretending to be The Poop Monster
- Saying curse words
- Putting barbecue sauce on chicken nuggets
- Making animal noises
- Dropping the F-bomb on people (especially Mario)
- Giving his pets vulgar names
- Melvin (Pee Pee Suck II/Poop Butt)
- His Giant Inflatable Duck
- Peeing on Mario
- His chop saw
- Mashed Potatoes
- Black Yoshi
- Painting on the fence
- SpongeBob Moves In App
- SpongeBob (his favorite show)
- His iPad
- His iPhone
- Destroying green beans
- Slapping women
- Chicken Nuggets
- French Fries
- Throwing cartons of milk, saying that they slipped
- Mickey Mouse
- Chef Pee Pee
- Roast beef
- Pizza Hut
- Beating his meat
- His drawing self
- Toys R Us (formerly, due to bankruptcy in 2018)
- Ice Cream
- Froot Loops
- Lucky Charms
- Poopy Butt (Formerly named: Shitass)
- Watching YouTube
- Jeffy Junior
- Five Nights At Freddy's (In Robot Jeffy)
- His Pokemon card, Politoed EX
- Taco Bell
- Rocket League
- Bananas the Gorilla
- Dudely Awesome
- Gorillas (possibly sexually)
- Hershey's chocolate syrup
- Jimmy John's
- String Cheese on his green beans
- Beating up Bully Bill
- Bumble Bee Shoes
- Video games
- Chuck E Cheese’s
- Being expelled from his school
- Lifesavers (candy)
- Picture of a finger
- Beary (his teddy bear)
- Cheese pizza
- Chocolate ice cream
- Spongebob toys
- Fortnite piñata
- Fortnite toys
- Chocolate ice cream
- Green Beans
- Being called a "bad boy"
- Animals (formerly)
- The Ticket Blaster (in Jeffy's Birthday!)
- The Bunny Do stopping
- Jeff The Killer ("hippopotamus")
- Pieces of gum
- Gummy worms
- Getting the flu
- Flu shots
- Being punished
- His shirt running away from him
- Getting underpaid for his teeth
- His helmet running away from him
- Nazi Cheeseburger
- Nancy (his abusive mom)
- Evil Bathwater Bubbles
- Taking a bath or shower
- Balloons popping
- Dead Bodies
- Being grounded
- People stealing his money
- Bully Bill
- Being called a retard
- Bullies not following the Anti-Bullying rules
- Losing his pencil
- Breaking his helmet
- The moon
- Creepers (Minecraft)
- Coal (which he mistakes for elephant poop in Jeffy's Bad Christmas)
- His bicycle being taken away from him
- Having a toy taken away from him
- Jeffy Junior Misbehaving
- Getting detention
- Scary Bunny
- Taco Bomb
- Tic Tacs (his allergy)
- Spiders (Minecraft)
- Having no Wi-Fi
- His helmet (In Jeffy's Switcheroo!)
- Summer school
- Military School (possibly)
- Being expelled (in Robot Jeffy)
- Getting raped (in Jeffy's Bad Word!)
- The numbers 6 and 7 (in Jeffy's Biggest Fear!)
- Pepperoni pizza
- Getting more homework
- Vanilla ice cream
Jeffy has been known to commit crimes. Being over the age of being arrested, these crimes could land him in jail.
Assault: In Jeffy The Rapper!, he smacks a woman and in Jeffy's Bad Christmas, he attacked Brooklyn T. Guy who was disguised as Santa Claus.In First Day Of School and Substitute Teacher! he threw random stuff at Jackie Chu and Mrs. Nutkiss. Jeffy's Imaginary Friend! He threw a chair at Jackie Chu. In Invisible Jeffy! He knocks out Jackie Chu and smacks 6 girls' butts at a beach.
Kidnapping: He, along with Junior and Cody captured Santa Claus and held him hostage.
Filing a false report: In Jeffy's Bad Word!, he lied to everyone that Mario raped him when in truth all he did was spank Jeffy.
Theft: As mentioned in Jeffy The Rapper!, he opened up someone's mail. In Jeffy The Rapper 2, he stole some of the prize money. He also stole a Lego man from Walmart in The Watch!. In Invisible Jeffy! he steals a sandwich in a restaurant that a man who works there was making and he also stole Goodman's money while he was searching for his wallet, causing Jeffy to be shot in the abdomen.
Vandalism: In Jeffy's Mistake!, Jeffy smashes Black Yoshi's Xbox one off the balcony although it was a dream. He also destroyed the switch console in Nintendo Switch. In Jeffy's Wifi Problem! he shattered the dishes Mario made him wash. He also destroyed the TV thrice: Jeffy's Tantrum!, Jeffy Gets Hypnotized!, and Jeffy The Psychic!
Bowser Junior's Nerf War! (possibly)
Jeffy's Mistake! (dream only) (Blown Up by Black Yoshi)
Jeffy's Flu Shot! (possibly, off-screen)
Jeffy Gets Stung By A Bee! (revived)
1 2 Switch Bodies! (possibly, off-screen)
The Golden Egg! (possibly)
Jeffy's Fidget Spinner! (off-screen)
Jeffy Has Hiccups! (Mario's imagination only) (Holding Breath for too long)
Jeffy's Taco Tuesday! (off-screen) (Threw explosive tacos on the couch, killing himself, Mario, and Cody)
Jeffy's Energy Drink! (revived) (heart failure)
if SML gets Ads back! (joke only) (Burned by his creator)
Ghost Jeffy! (revived) (choked by lifesavers candy)
Forms and Variations
Sick Jeffy is Jeffy with the flu, taking way greater effect than normal would with other characters such as Mario, and having a chance of giving others the flu. His appearance also changes to rundown, tired, and overall extremely droopy. The puppet was made by a fan known as Matt'zStudioz. This version of Jeffy appeared in Jeffy's Flu Shot!.
Smart Jeffy is a variation of Jeffy, appearing in an episode of the same name, who is incredibly smart compared to his normal form, due to his pencil having impaled his brain because of a freak accident indirectly caused by Junior. However, at the end of the video, Jeffy sneezed, blowing his pencil out back down his nose, leaving a hole in his brain, and reverting him to his normal form.
J-FeeA rapper variation of Jeffy that sings the songs "Why?" and "Wanna See My Pencil?."He has gotten arrested twice; the first time for shooting an elderly woman and opening up somebody's mail, the second time for slapping a girl. This version of Jeffy appeared in Jeffy The Rapper!, and Jeffy The Rapper 2.
Emo Jeffy is a more depressed version of Jeffy with gothic-looking clothing and hair. This variant appeared in Jeffy's Tantrum!.
Green Bean Jeffy
Due to the Green Bean Giant being angry at for not eating green beans, he cursed Jeffy and transformed him into a human-size green bean. The curse eventually wore off after Jeffy ate a whole plate of green beans, reverting him to his normal state. This is the primary reason why Jeffy no longer complains about green beans until Jeffy's Cat Piano Problem!. This variant appeared in Jeffy And The Beanstalk!
Redneck Jeffy is a variation of Jeffy with a Redneck's brain in his skull. After Jeffy sneezed his brain out, the doctor accidentally dropped his brain in his recycled brain bin, and they had to spend 8 hours picking out random brains, one of the brains was the Redneck's brain. He wears a Sombrero, rattles a Maraca, and talks in a Southern accent. This version of Jeffy appeared in Jeffy's Brain!.
Drawing Jeffy is a clone of Jeffy that he accidentally created by saying "Doodle doodle pencil fart!". Junior traps him into a piece of paper, and he is not seen until Jeffy Sneaks Out!, where Jeffy accidentally revives him with Play-Doh. He is shot and killed by Mario. This is the variation of Jeffy that has had the most appearances. The puppet for this version was made by a fan.
Jeffy App SalesmanAlthough not a form or variation of Jeffy, it is an identical person, looking and talking exactly like him, aside from wearing Marx glasses. This version of Jeffy appeared in Jeffy's Tantrum!.
Jeffy turns way more angry than usual after eating tic-tacs. He gets so mad that he even shouts at Junior, who is one of his best friends. It looks like the normal Jeffy, but with big slanted eyebrows. He appears in Jeffy Gets Help!.
Jeffy's face gets really messed up, similar to Drawing Jeffy. However, he is black and white and is suicidal. This form's Jeffy isn't energetic like his normal self. This happened after eating tic-tacs. The puppet for this version of Jeffy was made by a fan. He appears in Jeffy Gets Help!.
Wig JeffyJeffy has lots of overgrown "hair" that needs to be cut. After Mario sees him, he goes to call a Hair Cutter to cut Jeffy's "hair". Before he cuts it, Jeffy shakes his head, revealing that it is actually a wig.
Jeffy dresses up in his taco suit. His appearance is a standard hard-shelled taco with meat, lettuce, and cheese. Jeffy asks Mario to buy him tacos from Taco Bell because it's Taco Tuesday. Jeffy's body can still be seen behind the taco, with Jeffy's head sticking through the front of the suit.
For More information check out Scooter
Scooter was a clone of Jeffy. He was made by Cody's cloning machine (or C-C-C-Cloning machine). They had a short relationship with each other as he was shot in the face with a Nerf gun by Bowser Junior only minutes after he was made.
MarioMario is Jeffy's adoptive father. Mario has an apparent strong dislike of Jeffy, but deep down, he actually deeply cares about him. This is pretty much confirmed in Jeffy's Parents! However, Jeffy likes Mario. He usually calls Mario "Daddy". Mario finally adopted Jeffy after a year in Jeffy's Parents!. Mario was incredibly unhappy that Jeffy was dropped off at his apartment door and loathes the fact he has custody of Jeffy. Mario gets frustrated with nearly every video they appear in together. Most of the time, however, it seems that Jeffy annoys Mario, not on purpose. Mario had tried multiple times to get rid of Jeffy, but to no avail. Most of his attempts ended with Jeffy back at Mario's step or in the case of Where's Jeffy?, Mario going back to get Jeffy because he had Rosalina's necklace, only to find out that gave it to a squirrel. In Bowser Junior's Nerf War!, both Mario and Jeffy even made a small cameo appearance right at the end and Mario attacked Jeffy with a Nerf gun. Jeffy gets Mario into trouble often. Mario used to hate Jeffy in earlier episodes, but he deep down loves him, except for his stupidity. Although Mario gets annoyed with Jeffy most of the time, he has been shown to care about Jeffy, as shown in Jeffy's Mistake! when Black Yoshi was about to kill Jeffy; in Rosalina's Parents!, Mario gets scared when he assumes Jeffy fell to his death and freaks out when Jeffy gets abducted. It's possible Mario might only care just so Rosalina won't break up with him. Despite all this, they deep down love each other.
Considering how widely popular and relevant both characters are, Jeffy and Bowser Junior are very good friends. They enjoy hanging out with each other and make a good team. When both Jeffy and Junior met for the first time in Bowser Junior's Game Night 3, Junior called Jeffy awesome for surviving a game of Russian Roulette. Jeffy was indirectly also the reason for Mario and Junior permanently recognizing each other starting from that episode, and he also seems to like Junior. As of recently, both Junior and Jeffy seem to get along more, as shown in Shrek The Babysitter! and Smart Jeffy. Junior even caused the main plot elements of Smart Jeffy and Jeffy Loses His Teeth!, wherein he made a jump from a trampoline and hit a table in the former, and accidentally knocked one of Jeffy's teeth out with a T-ball bat in the latter.
Jeffy's mom, whose name is Nancy, debuted in Jeffy's Parents!, and she was shown to be very abusive towards him, to a much higher extent than Mario was. Nancy acted like she cared about him when people were around, but when they were alone she would always beat him. Nancy eventually got arrested and Jeffy ended up getting adopted by Mario. The original puppet was made by Evelinka from Beacon Art Studios (Eva Gronowitz).
Jeffy and Rosalina seem to get along well, especially on Rosalina's side. She copies Jeffy a lot. Jeffy usually calls Rosalina "Mommy" just like how he calls Mario "Daddy". Rosalina acts like a deep motherly figure to Jeffy, to the point of sometimes caring more about Jeffy, and calling Mario out whenever he abuses Jeffy, even breaking up with Mario when he heartlessly let Jeffy go with Nancy. He will yell at her occasionally if he does not get his way.
Jacques Pierre François
Not much is known about Jeffy's relationship with his dad, world-renowned French painter Jacques Pierre François, who had died after committing suicide in pursuit of his art. Due to the fact that Jeffy's "IF LOST" paper contains Jacques's name and address information, this could imply that Jacques used to care about Jeffy. Jeffy has also claimed that he learned basic French from his father. The original puppet was made by Evelinka from Beacon Art Studios (Eva Gronowitz).
In Jeffy's Sister!, it was revealed that Jeffy has a sister named Feebee. Jeffy and Feebee are very similar in character, with nearly exactly the same traits. They can even communicate to each other through diaper patting, somehow. However, it was revealed in Jeffy's Sister Returns!, that Jeffy's sister Feebee was killed when she got hit by a truck while riding a bike and died back in 2015, three years ago. The original puppet was made by Evelinka from Beacon Art Studios (Eva Gronowitz).
Brooklyn T. Guy
Most of the time, the Brooklyn Guy doesn't seem to mind and cares about Jeffy, as shown in episodes such as Mario The Babysitter!, Jeffy's Bad Word!, Jeffy Goes To The Zoo! and Locked Out. However, in the third episode of Who Wants To Be A Millionaire?, Brooklyn Guy is shown to get annoyed with Jeffy's behavior.
Chef Pee Pee
Jeffy seems to like Chef Pee Pee. Chef Pee Pee, however, does not seem to have the patience for Jeffy, almost as much as Mario; for instance, he got annoyed with when Mario and he were trying to get to eat his green beans. Chef Pee Pee also seemed upset when ruined the pencil cake Chef Pee Pee made for him. When Chef Pee Pee babysat Jeffy, he was so annoyed by Jeffy's shenanigans to point that he was would've killed Jeffy if Mario hadn't showed up in time.
Black Yoshi and Jeffy has only unofficially met in one video Jeffy's Mistake! but that video however is just a dream. However, Black Yoshi and Jeffy has mention each other many time in later episodes like Jeffy's Piggy Bank! and they seem to rather have more of a positive relationship rather than a negative one. Jeffy doesn’t seem to have much of a relationship to Black Yoshi.
Jeffy and Shrek don't seem to have a good relationship because Jeffy locked him in the bathroom and ate his cheesecake along with Bowser Junior so Shrek locked both of them on the bathroom with the toilet clogged.
Jeffy and Toad seem to be rivals when it comes to the rap game, however outside of rapping, for the most part they seem to be on good terms. Even if they don't have much interaction outside of rapping.
Jeffy is a frequent target for Bully Bill. However, Jeffy does not take it lying down, and turns Bully Bill's bullying on him with extreme physical violence. Despite the number of beatings he has taken, Bully Bill never learns his lesson.
Not much is known about their relationship, other than they don't like each other.
Jeffy is known to be the most controversial characters of SuperMarioLogan. Many fans complained by saying that Jeffy is offensive, due to him being a stereotype of mentally disabled people. Later, Logan claims that he is meant to be funny like Chef Poo Poo, not mentally disabled. Since Jeffy's Bad Word! and Locked Out was released, Jeffy received an immense hatred from older fans, because of him saying the word "faggot" and being an absolute jerk towards Mario. Despite this, he is also known to have a diehard fanbase, which consists of young children and teenagers and adding even more controversy. After Jeffy's Parents!, many people started liking him as he had been abused by his mother, Nancy. Jeffy's popularity grew when Jeffy The Rapper! and Jeffy's Fidget Spinner! was released, which made many young children grew fond of Jeffy and worshipped him. Later, the children constantly demand more videos featuring their favorite character and will dislike any video that does not feature him. This caused many older fans to fuel their hatred for both Jeffy and his fanbase. In Jeffy's Fun Day!, he received a poor reception. In December 2017, a seven year old child attempted to hang himself with a noose-like Jeffy did in his emo form in the now-deleted Jeffy's Tantrum!. The mother of the child discovered this and reported in the news after he attempted to do the act. Logan then apologizes and assures that his videos are not to be imitated. A few months later, a third grader watched Jeffy The Rapper! and gets disciplined after mimicking him. As of late 2018 and early 2019, SML lost some of his viewers, due to the fact that Jeffy became overused and incredibly popular with young children, even though Jeffy's actions and language are inappropriate for their age.
Abilities / Super Powers
Magic / Flight
- Logan has confirmed in a Chilly Vlog that he is going to take a break from using Jeffy, as he has caused his channel problems since his debut in Mario The Babysitter!, however, Jeffy will return sometime soon again.
- Jeffy appeared in Jeffy Plays Baseball!, confirming he was neither “axed” or put on a hiatus.
- It's revealed in Jeffy Gets Help! that Jeffy is allergic to Tic Tacs.
- Jeffy's favorite foods are carrots and chocolate cake as revealed in Lance's Character Q&A video.
- He also likes pancakes with marshmallows.
- He is the only character to debut in Season 8 that is still in the show.
- According to Logan, the Jeffy puppet's pants are sewed on. Any time he is seen naked, he is shown either from the waist up or a stunt double is used.
- Jeffy likes Mashed Potatoes.
- Jeffy's full name; Jeffy Jeffy is a reference to Mario's full name; Mario Mario
- It has not been confirmed if Jeffy is mentally disabled and retarded.
- In Jeffy's Homework!, Jeffy is revealed to attend "Special Needs School", despite the fact Logan has said Jeffy is not disabled. This has since been changed to Jeffy attending the same school as everyone else, suggesting that he is simply extremely unintelligent rather than mentally retarded.
- In Jeffy Gets Bullied!, it is revealed that Jeffy's belief that 8-4=8 is now being taught as fact, under the name "Jeffy's Law of Mathematics.".
- He also thinks 2+2="Baby 2", 0+0=2 and 9+3=93.
- Jeffy's original address is 7 Jeffy Street, Paris, France.
- He has been constantly abused by Nancy, his mother (which in turn may be the reason for him treating Mario badly).
- Jeffy is 14 years old and is of French descent.
- In the Pokémon series, Jeffy owns a Cookie Monster and somehow taught it Thunderbolt.
- Despite being slightly unintelligent, Jeffy is still able to do many impressive acts, such as accurately painting the Mona Lisa on his Easter egg, finding a golden egg even though Mario threw it away, saying the full alphabet backwards, and getting random articles of clothing out of thin air.
- Jeffy is first seen without his helmet in Where's Jeffy?.
- Jeffy sometimes speaks normally, and sometimes in 3rd person.
- Jeffy has many different poses in the videos' custom thumbnails.
- His theme song is Doh De Oh by Kevin MacLeod.
- In Jeffy's Birthday!, it is revealed that Jeffy's birthday is on August 21, and his birth year (2004) was revealed in Jeffy's Parents! after the other half of his "IF LOST" paper was recovered.
- The original puppet was made by Evelinka from Beacon Art Studios (Eva Gronowitz) the puppet can be found on the Evelinka @Etsy website. The puppet on Etsy costs between $275 to $500.
- Jeffy is seen with his eyes bulging in Jeffy's Stupid Home Video!, Jeffy Sleepwalks!, Jeffy's Birthday!, Jeffy's Sister!, and more (including one eye).
- From September 22, 2016, until September 27, 2016, SML was selling T-shirts for $19.99 USD and $26.11 Canadian dollars. This was revealed in Jeffy's Sister!. However, this could've been-replaced by the sml merch store.
- In First Day Of School!, Jeffy is shown to be in second grade, leading many people to assume he was 7 or 8. Despite being 13 years old, it could be possible Jeffy has been held back 6 or 7 times.
- It is possible that Jeffy puts his pencil in his nose because Jacques Pierre François got famous for putting paint in his nose and sneezing it out.
- In Jeffy's Bathtime!, it is revealed that he has aquaphobia, a fear of water.
- Eleven seconds in, you can see a possible early version of Jeffy in the SuperLuigiLogan video, Puppet Closet! This puppet was used for Timmy in The Christmas Special!.
- Because of his lack of intelligence and dimwitted behavior, it's possible his mother never take him to school before he was forced to move with Mario in his apartment.
- Jeffy has changed quite a bit since his first appearance in Mario The Babysitter!.
- Jeffy used to bang his head on the nearest surface whenever he was called a bad boy, but this seems to have subsided.
- In earlier videos, he was unaware that his pencil was in his nose. In recent videos, he knows that his pencil is in his nose.
- In earlier videos, whenever he would pat his diaper, he would not respond to anything, though this has changed.
- In his first appearance, his voice sounded way more different than his new recent voice from April 2016.
- He used to put other things besides his pencil up his nose, but he later stopped doing that.
- He used to hate green beans and refused to eat them. However, Jeffy promised to eat his green beans after Jeffy And The Beanstalk!.
- However, Jeffy still hates green beans and broke his promise to Mario in Jeffy's Cat Piano Problem!.
- Jeffy became 13 (a teenager) on the same day of The Great American Eclipse.
- It is also revealed in Jeffy's Birthday Wish! that his birth sign is Leo.
- On November 22, 2017, Logan uploaded a video on Chilly's channel saying that he'll make some minor changes to Jeffy, as YouTube kept on demonetizing videos that have to do with Jeffy doing inappropriate things, like humping a Cheerios box and swearing most of the time.
- Smart Jeffy is the second character to solve a Rubik's Cube, the first character being Cody.
- Jeffy is now the most used character in the SuperMarioLogan channel.
- Logan has also stated in an interview with dabhdude that he wishes that he had never added Jeffy, due to the issues that have arisen after his debut. However, in SML Reacts: Jeffy's Mistake, he does admit to liking Jeffy as a character.
- Jeffy was not originally meant to always spank his diaper. It was in Mario The Babysitter! where Lance started to make Jeffy spank his diaper out of nowhere. In fact, Logan was originally going to cut the scene of Jeffy spanking the diaper since it makes him seem like he's jacking off but however, the majority of the cast members starts dying of laughter so Logan decided to put it in instead and is thus why Jeffy often spanks his diaper in his older videos and even some of his newer videos.
- As announced in a Chilly vlog, Logan might not make Jeffy in SML videos anymore, that is until Jeffy Plays Baseball! appeared.
- It is revealed in Jeffy Goes To The Zoo! that Jeffy May be a gorillaphile.
- His favorite food is chocolate cake and carrots.
- In Lance Thirtyacre's Meet the Cast video, it is revealed that Jeffy was originally going to be named Doofy, however, they already had Doofy The Dragon, so they ended up with naming him Jeffy.
- Coincidentally, both Doofy and Jeffy are played by Lance and have somewhat similar voices.
- In Meet the Cast video it's revealed he was originally going to be voiced by Pablo but due to voicing Brooklyn T Guy he couldn't voice Jeffy since it would be hard for him.
- Jeffy was actually supposed to have a red helmet but never happened.
- When they first got Jeffy he never had a diaper, pencil in his nose and didn't have the name Jeffy on it.
- He wears a Up & Up newborn diaper.
- Jeffy prefers cats over dogs as revealed in Lance's Character Q&A video.
- He wants to be a grown up when he grows up.
- It has been revealed that Jeffy has passes Second grade 
- It was speculated by many old fans that in his original personality Jeffy was a replacement for the beloved early-generation characters Mama Luigi and Tony The Tiger, because of their dumb antics. In later videos however, Jeffy's personality has changed in a way Mama Luigi and Tony never would have acted, disproving the theory that Jeffy was Mama Luigi and Tony's replacement.
- He can't swim, as revealed in Jeffy Plays Baseball!.
- Jeffy's favorite color is a carrot as revealed in Lance's Character Q&A video.
- Jeffy's favorite character on Spongebob Squarepants is Patrick, however he believes that Patrick is Squidward.
- Jeffy's way of understanding people is the opposite of his objective.
- It is shown in "Jeffy's Bathtime!", that Jeffy may have hydrophobia, a fear of water.
- Jeffy is a fan of Naruto.
- Based on his statement in Bowser Junior Kinda Goes Camping!, it is possible that Jeffy is the way he is because he has Down syndrome, since he states "I'm down...syndrome.".
- He swears like Goodman.
- It is revealed in Lance's Character Q&A video that the reason Jeffy spanks his diaper is because it "feels good on his pee pee".
- Due to him being cross eyed, Jeffy can look both ways at the same time when crossing the street.
- Due Jeffy having used the Memory Looker Backer Machine to help finds his pencil in Jeffy Loses His Pencil!, Jeffy is now at an increased risk for brain cancer.
- Jeffy has admitted that even though his name is written on his shirt, he still forgets his name sometimes.
- Jeffy has a rod that is usually on his left hand, so Jeffy might be considered left-handed
- In Lance's Character Q&A, Jeffy is asked if he has laughed, and he says he never laughed. Which is not true, since Jeffy in First Day Of School! You see him laughing with Junior, when he put on his name card "Poopy Butt", and in Jeffy's Trap!, Jeffy is seen laughing. Maybe Lance did not remember those episodes and that's why he answered that.
- Jeffy doesn't know his colors.
It has been confirmed by Logan in a Chilly vlog that when SuperMarioLogan gets ads back, he will make a video where he burns the Jeffy puppet outside for all the trouble he's caused to both SuperMarioLogan and SuperLuigiLogan, and will kill the character off. He's also stated that when he gets ads back, he will upload the long-awaited SuperMarioLogan Movie and will upload Bowser Junior and other characters’ videos.
This however was later confirmed to be just a joke. Logan has keep saying many times that he will kill off Jeffy but he always jokes about it, meaning Jeffy is still alive.
Logan has release many new merch with most of them being Jeffy related like the Jeffy phonecase, Jeffy T-shirt and the newly added most wanted being the Jeffy Puppet which cost approximately $99 which have currently gem discounted to $75. Most of the shirts and stuff there tend to be pretty pricey ranging from $20-$50. The Jeffy Puppet tends to be the most popular sidling about 80 puppets PER DAY. The Puppet according to Logan is a 24 inch Puppet made from plush fabric outer layer, 100% Polyester inner layer for hand-insert, stuffed with PP cotton. PU leather shoes, and non-woven diaper. The production takes up to 1 or 2.
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- ↑ 1.0 1.1 Jeffy's Parents! (https://www.youtube.com/watch?v=h1iAdAGtCHY)
- ↑ Jeffy The Rapper! (https://www.youtube.com/watch?v=VF3N0pEIM2s_)
- ↑ First Day Of School! (https://www.youtube.com/watch?v=wsPA_yOq-iU
- ↑ The Fender Bender! (https://www.youtube.com/watch?v=y0tvZTR1ar8)
- ↑ Jeffy Gets a Job! (https://www.youtube.com/watch?v=sCJVUFW-dpY)
- ↑ https://www.youtube.com/watch?v=6O2184Q2wFY
- ↑ "Jeffy's father is Jacques Pierre Francois". However, Jeffy's last name is now Mario, hence the né
- ↑ Jeffy gets adopted by Mario in Jeffy's Parents!.
- ↑ Rosalina marries Mario in Mario's New Hat!
- ↑ Substitute Teacher!
- ↑ See https://www.youtube.com/watch?v=aaW9vUwEJyY and https://www.youtube.com/watch?v=pX6vby0AEoM
- ↑ "Logan Reacts: Mario The Babysitter!" SuperLuigiLogan. YouTube. March 7, 2018.
- ↑ https://youtu.be/5LMuUaBevuE "Jeffy’s Summer School"SuperLuigiLogan. YouTube Jul 4, 2018.
- ↑ Jeffy Gets Help!
- ↑ Jeffy's Imaginary Friend!
- ↑ Jeffy's Birthday Surprise!
- ↑ Jeffy Loses His Pencil!
- ↑ Jeffy The Psychic!
- ↑ "Logan Won’t Burn Jeffy Unless " Chilly. YouTube. July 14, 2018.