About this Simpsons episode:
The Simpsons - Double, Double, Boy in Trouble is the third episode of season 20 and number 423 overall in the series.

Bart meets the rich Simon Woosterfield, who happens to be Bart's exact look-alike and is a member of Springfield's richest family. As a prank, the two decide to switch places / homes; Simon enjoys his time with the Simpsons while Bart discovers his rich new half-brother and sister are out to kill him, so they can inherit the vast Woosterfield family fortune. Former NFL football great Joe Montana guest stars as himself.