Mun is 18+, and Crowley is more than a couple hundred years old.
He is played circa season 5 by default, usually a bit more involved than canon for CR reasons. He's a prat, especially if he likes you.
He also comes in an AU flavor with rather large black wings as a gag by Gabriel for being decidedly nice for a demon. They seem to be a rather permanent fixture, much to his annoyance.
There's also an AU flavor where he is a fallen angel corrupted into a demon. Not much is different, aside from the obvious. As an angel his name was Crosiel. His thing about claiming to have been a tailor that sold his soul for a bigger dick is kept as true, save that it was a bit of an elaboration.
Slash goggles always on -- c'mon, it's Crowley. Cas/Crowley is love, but he's played with most any creature he finds attractive. Ie, pretty much any male character of note in SPN. Crossover friendly for all your soul-bartering needs.