Pretty much anything if we're talking about the general setting, though I usually prefer great freedom in the chosing of characters, so I tend to join RPs with high fantasy components. But now? I feel like nigh-anything will do (save slasher/splatter horror and stuff like that), I'm even willing to try my hand at romantic writing if it means I get something more to do.
Oh don't worry, I don't watch Naruto, out of a few episodes I snagged while channel-surfing. My point is, wear loose clothes (bottoms, not uppers) and slightly improperly aligned as to conceal the real position of your other cheeks, or something else to protect them like going the flip side entirely and wearing a tight cloth pair of pants or such. Believe me, if I could find the page detailing the prank, I'd do so, but that'd likely scar your soul.
EDIT: Found it, it's called
kancho.
'Tis alright, no big deal