def.: a comic imitation of another's work that is often intended to criticize the original
A parody should do much more than make readers or viewers laugh at the original—it should highlight aspects or point out flaws in the original that people would not have seen otherwise in order to help them get a more rounded perspective. (The Colbert Report, anyone?)
Another example, which I was alerted to by Language Log,* includes the Miss USA contestants' answers to the question, "Should evolution be taught in schools?" The parody asks, "Should math be taught in schools?" and by doing so, highlights some of the flaws of the evolution vs. creation jargon that has become accepted in the for/against debate. It's pretty funny, too.
The original (no need to watch it all; three or four minutes will give you the idea):
And the parody:
*Language Log discussed how the expression "to believe in" something is used in general, based off the contestants' answers to the question.