Was a MUD instead of a MUSH, but hopefully those still count.
Anyway on Realms of Despair I had run across a lot of other thief characters that were the last surviving member of some town or village, or were just abandoned to the streets and in general were dour, and angsty folks.
So I made a pixie thief, who ran away from home to join the circus. Realized after a year the circus sucks, and went to go live in the city. Lacking any other skills needed to start a business in the city, like carpentry, or mercantile sense... or hell even common sense, she just took to taking things that looked like she could trade them for food and places to sleep.
II had a lot of fun with that character. Super friendly, cheerful and helpful, happily talking with anyone and everyone about anything she could... while disarming traps, or gouging out the eyes of their enemies. I mean you don't survive being only 2 feet tall in the streets without learning something about being terrifyingly vicious.
Always got a kick out of people being unsettled by her gleefully talking about this awesome new place she found that sells candy... while just completely covered head to toe in blood.
It's not that she LIKED killing things, she just didn't see why she should feel bad about killing someone that wanted her dead.