Instead of faking a plausible excuse, a person tells an audacious lie in order to make it known that they just don't want to hang out with you, presumably in order to offend you enough that the situation won't occur again.
Jake: Hey man, you wanna go catch a flick at the old drive-thru?
Ruler of Lake Titicaca. Rumored to have a bunghole that gets very angry if it does not receive toilet paper. Cornholio the Great is often seen walking around with his shirt over his head and his hands in the air, chanting songs about his power, and his bunghole.
"I am Cornholio! You do not want to face the wrath of my bunghole, for I need TP!"
Butthead: Shut up, Beavis! (uh huh huh huh)
Beavis: Um, okay. (heh heh heh heh).