What movie is this? Please help!?

ok so i saw this movie when i was like 7 (im 11 now) and i cant remember what its called: its a nickelodeon movie about a boy who goes to like an amusement park with his friends and they make him hold all the prizes they won at the booths while they go on the rides. then the boy runs to catch up to them and gets hit by a "train" and go flying. he wakes up in the ER and finds out he has to get a brain transplant from this famous guy (i think his name is milton) who created all these cartoon characters. so after the transplant he hallucinates all the cartoon characters who the guy invented and they talk to him and he becomes famous for having his brain. and so thats pretty much all i can remember.