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Mario, Rosalina and Jeffy are sitting on the couch. Jeffy starts trying to make himself throw up, and when Mario asks why, Jeffy explains that he is bored. Rosalina suggests that they play hide and seek. Mario tells Jeffy to count to twenty, but he is only able to count to five. Mario and Rosalina hide under Jeffy's crib. Rosalina thinks the spot is to hard, but Mario disagrees. However, Jeffy still does not find them after three hours, and Mario and Rosalina fall asleep. When they wake up, they decide to check on Jeffy.
Jeffy is still trying to count to five. He claims that he is trying to learn the alphabet, but he needs a tree to do so. Mario gets mad at Jeffy for not looking for them. Rosalina suggests that Jeffy should instead try to hide instead. Jeffy then looks for a place to hide, but he hears knocking coming from the door that they are not allowed to open. He finds the door, opens it, and screams. Mario and Rosalina hear the scream and run to check on him.
Screaming ensues as Mario, Rosalina, and Jeffy find 26 dead puppet bodies residing in the room the door led to. Rosalina and Mario proceed to call Brooklyn T. Guy for help, and they show him the room, only for Brooklyn T. Guy to knock Rosalina, Mario, and Jeffy out.
After Mario and Rosalina wake up, they realize that they are chained up, with Rosalina's mouth taped shut. It is revealed that Brooklyn T. Guy killed all the people in the room and continues to slaughter those who cannot follow his only rule.
Brooklyn T. Guy then reveals how he got out and managed to help Mario and Rosalina with their problems, shortly before slaughtering a body with a chainsaw, much to Mario and Rosalina's shock. Brooklyn T. Guy then gives Rosalina a hammer to the head after she keeps annoying him, and threatens to do the same thing to a traumatized Mario. Brooklyn Guy then cuts open a body's mouth and gets rid of the brain. Just as Brooklyn is about to murder her, he is shot and killed by the real Brooklyn T. Guy. Brooklyn T. Guy then unchains everyone, tends to Rosalina's injuries, and calls the entire thing "really messed up". He explains that the Brooklyn T. Guy from the room was actually his twin brother, Does Bad Things Guy. Does Bad Things Guy was a temporary replacement as he went on vacation for 7 months up to the point where he conveniently returned to save Mario & Rosalina. After Brooklyn leaves, Jeffy states why he went in there and his reasoning behind it was that a guy was "suffering" and "died", much to Mario and Rosalina’s confusion.
- Does Bad Things Guy (final appearance and death)
- Bowser Junior (Deleted scene)
- Brooklyn T. Guy
- 26 Unknown People
- Brooklyn T. Guy Junior (dead body)
- Bowser (flashback)
- Chef Pee Pee (cameo as a police or a error)
- Does Good Things Guy (mentioned)
- Miami Guy (mentioned)
- Philadelphia Guy (mentioned)
- Sonic the Hedgehog (Deleted scene)
Logan had stated in a Chilly blog the video will feature Junior and Jeffy, who do not know about the door and decide to open it. (Brooklyn T. Guy is the only one who knows what's in there, besides the 26 murdered people) Then, Logan said that the boys would have gone to tell their dads, Chef Pee Pee, and Rosalina to tell them what's in the door in which they all go explore and that's when Brooklyn T. Guy attacks them and knocks them out. Then there would be a struggle and a rescue mission. Logan said that what's in the door would never be revealed until the video was made.
According to Amanda, Chilly's cousin, who reacted to what was behind the door, had a scared reaction. This could imply what's in there is probably scary. Logan and Chilly also showed a few lucky fans what was in there, although it is possible that the what was behind the door was changed, since Logan said it would be uploaded by a deadline of May 10 because he couldn't think of any good ideas for what could be behind the door.
The video was released on May 10, 2017. If the video did not get released then, Chilly will show what's in there on her channel, and Chilly's brother Tito's mustache would be cut off. As a result, Logan had to rewrite some scenes and scrap some characters like Bowser, Chef Pee Pee (Lovell didn't want anything to do with the secret door) and Bowser Juinor (Logan couldn't easily voice two characters at once within the deadline).
During production, during Brooklyn T. Guy's entrance, he had an additional bit of dialogue that was cut. After asking if everyone was alright, he then states, in his normal, deadpan manner, that the question is stupid. This was likely cut to keep the tension up. The cut dialogue was seen in the BTS video.
YouTuber GamecubeDude300 knows a secret about the door from Anthony Miller, one of the former cast members in the SML crew, but he promised Anthony that he wouldn't reveal it to his fans. Despite this, Anthony still reacted to the video on his channel. GamecubeDude300 later said that the secret Anthony told him was that the secret room was used as a filming location for Happy Halloween! (see Trivia).
Many of the dead bodies were puppets of past characters that Logan deemed surplus, including King Strongbottom, D-Money, Brooklyn T. Guy's Wife, the Russian Spy, Logan's puppet likeness, and other, generic puppets, many of which were hacked to bits, meaning these puppets won't be used again. The gore was a combination of fake blood, Play-Doh, and real beef.
After the video was released, Logan brought up in a Chilly vlog the idea of making a Junior version of the Secret Door on July 10 where it would be nearly identical to the original video, but have Juinor, Bowser, and Chef Pee Pee instead of Jeffy, Mario, and Rosalina respectively. This idea was eventually later cancelled in favor of releasing Sunken! as Logan later changed his mind and didn't want to do with the Secret Door anymore.
On June 25, 2017, Chilly released a vlog showing what had become of the room after the video; it is now used to store the larger props. She also confirmed what Logan said originally about the room in New House Tour! that the room was originally an attic, but that when Logan moved in, he turned it into a room and added the door. However, Chilly also revealed that the original entrance to the room was located in the garage and that it's still there but is blocked off.
On January 9, 2019, Logan took delivery of new puppets to replace the ones hacked up for the video.
- This is said to be one of the darkest and disturbing SML videos ever to be released.
- In the end of the video, Brooklyn T. Guy says that what Mario, Rosalina, and Jeffy met in the secret door and it was DBTG. Some fans are confused about where was the real Brooklyn T. Guy. He saids that he needed a long vacation for unknown reasons and ask someone to take his place of helping Mario and the gang.
- Logan first said that this video will be uploaded in early April, but it didn't and Logan later promised the video will be uploaded in May, because he couldn't think of any good ideas for what can be behind the secret door.
- There are thousands and thousands of fan theories relating to the door and past SML events in the YouTube comments.
- Despite Logan hinting at Junior's appearance, Junior did not appear in this episode.
- The part where Mario and Rosalina fall asleep in the middle of the hide-and-seek game due to Jeffy taking so long is an allusion to the Connie the Cow episode where Connie didn't know how to count to play hide and seek, so Grouch and Wally fall asleep.
- This video was first teased at the end of Bowser Junior's Big Spill!.
- This video was one of the most hyped videos in SML history. Some hyped videos in the past include Jeffy's Parents!, The New House!, and the upcoming SuperMarioLogan movie.
- The video has been so hyped that, shortly before the release, Chilly, as well as many other people, held live streams counting down to the video's uploading. Chilly's live stream even showed the video being uploaded to YouTube on a MacBook.
- It is revealed that the 26 bodies mentioned in The New House! are behind the door. It is also revealed that, for the past seven months, Brooklyn T. Guy has been on vacation, and had his identical twin brother, Does Bad Things Guy, cover him, but thought the worst he would do is steal, rather than murder.
- The Three Military school students appear as dead bodies in this episode, implying that Does Bad Things Guy may have been the Sergeant Master from Bowser Junior Goes to Military School!; which might explain his villainous actions.
- Technically, 25 of the 26 victims first appeared behind the door because the 26th victim was found back in The New House!.
- It is possible that Does Bad Things Guy move the body of the 26th victim back into the room.
- This is technically the first appearance of Brooklyn T. Guy in 2017.
- This is NOT the only appearance of Does Bad Things Guy (This is really counting his appearance over the last 7 months, where he's been posing as Brooklyn T. Guy).
- If you count his appearances over the last seven months, this is technically Does Bad Things Guy's last appearance.
- In one of Chilly's vlogs, her and Logan do not use anything they had found at the multiple stores they went to get stuff for The Secret Door! which could possibly mean that there is an upcoming Secret Door sequel or Bowser Junior episode featuring Bowser Junior finding out about the door.
- The BTS of the Secret Door video on Chilly's channel is the first SML video to get age-restricted. Most likely because of going in detail on the gory content.
- A scene from Happy Halloween! was filmed in the room of the secret door before this video. When Junior and Cody get kidnapped by the clowns (around 9:17), the room they were taken to was the secret room. It obviously wasn't actually the secret room, just the same filming location.
- There is a BTS video on Chilly's channel.
- However, that video is currently age-restricted for unknown reasons. Maybe of the gore during the BTS. It could also be the fact Logan showed puppet. However, it's fake gore and blood.
- This is the goriest video since The Gun!.
- There are now 27 people who have been murdered in the house since Brooklyn T. Guy killed Does Bad Things Guy.
- However, 28 people have died there in total, as shown in The Magical Button!, another dead person is in the attic.
- The 28th person who died committed suicide to make up for the mistakes that they made with the wishes.
- However, 28 people have died there in total, as shown in The Magical Button!, another dead person is in the attic.
- The "body-meat" was ground-beef. It's also has make-up and slashed in-half body. And some chicken meat was used for some open wounds.
- Jeffy's Fun Day! was originally going to have Jeffy staring at the secret door for an hour, but Logan decided not to do that because it would break the continuity of Jeffy not knowing that the secret door existed.
- This marks the first appearance of Does Good Things Guy, as he kicked the door open killing Does Bad Things Guy, and saving Jeffy, Mario, and Rosalina.
- The whole psychological horror and slasher thriller concept is a reference to psychological horror and slasher thriller films like Psycho, the Halloween franchise, A Nightmare on Elm Street, also The New House! video with the first appearance of the door is a Mystery/Slasher like Friday the 13th (not the video Friday The 13th!)
- Zeke revealed in a video on his channel Zyoshiman, that Logan had initially planned to reveal Mama Luigi behind the Secret Door. They had difficulty having Zeke flying out to Florida (due to School and Work.) They eventually got him flown out (Shown in the Chilly Vlog SPECIAL GUEST!) But the idea was scrapped most likely due to time concerns.
- Despite it containing blood and gore, this video isn't age-restricted or demonetized.
- Stock footage from The New House! is used.
- This episode was uploaded 1 year after "Bowser Junior's Painting!", and 2 years after "Mother's Day!".
- As revealed in a Chilly vlog, Bowser Junior's absence is partly due to this deleted scene. Logan originally wanted to film a scene where Jeffy and Junior call the doctor. Does Bad Things Guy would then climb out the window and hold Mario hostage. This concept ended up being scrapped as Logan wanted to get the video finished in time to meet the May 10th deadline.
- Brooklyn Guy said that Does Bad Things Guy replaced him for seven months and that he killed 26 people in that time frame. Does Bad Things Guy gave the house to Mario in October which was 7 months ago, which means that Mario was the first person he gave the house too. Although it could be that Does Bad Things Guy sold the house in pairs.
- If the viewer looks in the background when Rosalina was about to die and when Does Bad Things Guy gets shot, the door opens and it is actually Chef Pee Pee in a cop outfit. This is most likely because Logan didn't have a spare Brooklyn Guy puppet (which explains why he reused the Brooklyn Guy puppet for Does Bad Things Guy).
- Brooklyn Guy said Does Bad Things Guy was his only identical twin. This is not true as Makes Bad Decisions Guy looks exactly like him in Jeffy’s Foster Home.
- At 7:55 after Does Bad Things Guy stops talking, his mouth continues to move. Even at 8:06 the same mistake occurred a little bit.