You know those Nigerian scam emails?
This guy got one asking him for $2000 in order to open an offshore account and get access to a fortune of 30 million dollars. He decided to reply and drive the sender nuts.
For 9 months he kept going back and forth, telling the Nigerians that he wants to help them, send them money, have them come live with him in his Florida estate... He even tried to scam some money out of the Nigerian (and almost succeeded!).
You can read the entire email correspondence (including a few voice mail messages) on the site. Although it may be a bit long, it is totally hilarious.
Eventually he created a two person "multi-media" comedy show about the correspondence that is apparently quite successful.