The Simpsons (1989): Season 21, Episode 6

21 - 6: Pranks and Greens

Fed up with Bart's constant pranks, Principal Skinner tells Bart that there is a former Springfield Elementary student hailed as the best prankster ever - even better than Bart - but he won't divulge the legendary student's name. Bart finally gets Groundskeeper Willie to reveal the prankster's identity: Andy Hamilton. Bart tracks down Andy, who is now 19 years old and hasn't grown out of his pranking days. Bart and Andy become fast friends until Bart gets Andy a job working for the ultimate clown.