Andrew Nestler has compiled a neat list of math and mathematicians on the popular TV show The Simpsons [wiki]:
Lisa dresses up as a boy to get into the boys' math class. The teacher writes the equation Y x Y = 25 on the board.
Teacher: Now, how many different numbers can Y be? Lisa as Jake: That's easy - just one, the number 5. Teacher: Wrong. [Lisa gasps.] Martin: There are two possible solutions: 5 and -5. Lisa interior voice: Oh my god, I was wrong - and by being corrected, I learned! [happily] And no one cared about my feelings!