Simpsons Season 5, Episode 18: Burns' Heir

Mr. Burns has a near-death experience which prompts him to find an heir to inherit his wealth after he dies. Bart is rejected, but Burns soon decides to choose him after seeing that Bart is "a creature of pure malevolence". Marge convinces Bart to go spend some time with Burns, and soon becomes more disruptive than normal to his own family and decides to go live with Mr. Burns.