| Please note the following:
He appears as a one time character. He appears after coming out of the Cheerio Box's 'womb'. Mario is disgusted to see him and refuses to become a grandfather. After pooping his pants, Jeffy teaches Jeffy Junior how to use the toilet. Jeffy Junior steps in the toilet bowl, turns on the toilet lever, and gets flushed to his demise, potentially drowning him.
From what is seen of him in Jeffy Has Kids!, he appears to be a complete outright idiot. He actually appears to be even more stupid than his father, Jeffy. He doesn't seem to be able to know how to talk, so he only grunts. He is a homemade fabric plush version of Jeffy but with Cherrios glued on his skin.
After Jeffy has conceived three children with a Cheerio box, he is born when the Cheerio box was given a C-Section. After the birth, Jeffy introduces his three kids named Pusshole 1, 2, and Jeffy Jr to Mario and Rosalina. Then as Mario is disgusted by how Jeffy Jr looks, him and his father pooped in their pants afterwards. Then when Jeffy Jr is grunting, Rosalina says that Jeffy Jr may be hungry. Then Jeffy takes him and Pusshole 1 and 2 to the dining table and fixes them a mountain of junkfood. Jeffy Jr then flips the food over, which angers Jeffy and prompts him to bring him into the room where Mario and Rosalina where. Then Jeffy spanks him until Mario and Rosalina stop him and tells him not to beat his kids. Then Mario requests sending Jeffy Jr to bed. Jeffy then leads Jeffy Jr to bed. Then Jeffy Jr wants to listen to a story. Then Jeffy tells him a story called "Goldief**k". Then after the story ends, Jeffy Jr poops in his pants, which angers Jeffy and it prompts him to take Jeffy Jr to the bathroom. then Jeffy puts Jeffy Jr in the toliet and tells him to stay in the toilet until he poops in it. Then the toliet lever activates by an unknown cause and flushes Jeffy Jr, drowning him. His brother and sister was also eaten alive by Bowser Junior.
- He was fan mail in one of Chilly's videos.