The Simpsons: 10 Hidden Jokes Everybody Missed
6. Mothballs In The Beef Stew
Bart showed off his softer side in the season 14 episode Special Edna after Principal Skinner's mother issues forced him to cancel a date with Mrs. Krabappel. In attempt to comfort his teacher, he takes her out instead.
This act of kindness earns him a mocking from Lisa, who asks “What happened to the Bart Simpson who put mothballs in the beef stew?”
No doubt most viewers took this as a reference to a prank that took place off screen, but the most avid fans of the show will know it's actually a line from the rap song Do The Bartman, a track the world has been trying to forget ever happened since 1990.