I met a gay guy last night.
Man, was he a pain in the ass.
Alright, listen up, buttercup. The joke here is that when someone says another person is a "pain in the ass," it usually means they're annoying. But, since this joke is about a gay dude, it could also mean that he was literally a pain in the ass. Get it? Probably not, you're probably the kinda guy who still uses internet explorer.