He is portrayed by Matt Knudsen.
He is first seen when Jimmy and his classmates are on a field trip to Gollyworld at Appleday Studios and Jimmy bumps into him, who is attempting to retrieve the brain from underneath the ice in Tux's Arctic Adventure. He chases Jimmy who Jimmy runs into a train and is severely injured and is sent to an on-premises hospital staffed by park staff who are also secretly certified physicians, where Milt's brain is transplanted into his head. He makes it out of the operation just fine with his personality intact but, he can now see all of Appleday's characters in real life (including Golly Gopher, Dolly Gopher, Tux the Penguin, Crocco the Alligator, and Pickles and Prickles), while no one else can.
Then, the cartoon characters lose their popularity thanks to Sonny who ruined them with his own ideas, Soon he was fired by the chairman.
Sonny learns about Jimmy having his father's brain and plots to steal it by moving in with Jimmy's family and renting out a room in Jimmy's house Sonny has dinner with them and meets Jimmy's alien sister, Yancy, all the while constantly scheming to get Milt's brain out of Jimmy's head and for himself. And without the brain, Jimmy would die. He devises a plan to modify Crocco's train to include several dangerous devices on it that will decapitate Jimmy and get him what he wants.
He later shows Jimmy around the office of Appleday Studios after he becomes president due to having Milt's brain and pulls a switch making a crusher crush the desk. Then he tries to electrocute Jimmy by making him sit in a electric chair but fails after he gets electrocuted himself.
Later on, the next day he returns home and Yancy catches him and scolds him for creating a robot to take out the trash instead of himself and it creates a mess and gets grounded by her.
Later after Jimmy leaves to host live at Gollyworld in Appleday Studios, Sonny comes from out the window at the top and reveals his plan to Robin (who was just told off selfishly by Jimmy) and kidnaps her and ties her to the tracks at Gollyworld so she would be ran over by the incoming train with several dangerous devices on it.
Soon as Jimmy explains about being tired of saying yes all the time, Sonny activates the train to try to decapitate him and explains his plan to Jimmy and about Robin being tied up to the tracks which makes Jimmy rush off to save Robin and Sonny tries to stop him but Jimmy's father Ken Roberts stops him and recognizes him as his wife and takes his mustache off.
After Jimmy saves Robin from the incoming train by turning into a cartoon and destroying the train with cold soup, Sonny catches up and chases Jimmy to Appleday Studios and looks for him. Then he sees Jimmy disguised at Milt Appleday and rips wires off a robot and tries to electrocute him but recognizes him as his father and is happy until Robin and Yancy catch up and meet Jimmy and Sonny and Sonny realizes that Jimmy is disguised as his father and tries to electrocute him but thanks to Yancy's powers, Sonny is teleported out of the studio, along with herself as she teleports herself as well.
Later, Sonny still wants the brain and is seen hiding behind a curtain. He has a device that can grab his head. Sonny almost succeeds, but the crane misses its target. He laughs evilly in the end, with Yancy telling him to shut up.
Out of Jimmy's Head
He returns in the Cartoon Network 2007 spin-off TV series, Out of Jimmy's Head where he still plots to steal Jimmy's brain but fails repeatedly due to his incompetence, or his plans going awry.
He is the sinister, villainous, and only son of Milt Appleday and had the nickname Booger for his odd and abnormal behavior. He has a very good evil laugh and announced his plans out loud that people around him catch on very fast and know his plans - which is the reason his plan failed. He is crazy and a crackpot and at the end shows that he misses his father very much, and seems to be very sad about the fact that his father is dead.
- He is the only child of legendary animator, Milt Appleday.
- He isn't very good at making cartoons and has been running Appleday Studios into the ground since he became president.