Chibi was a nickname back in HS, me and my older cousin went to the same school and I was basically a little version of him (we looked just like brothers) so his group of friends used to call me Chibi-Dragon (since they called him Dragon) then it was shortened to just Chibi, and it stuck.
BlackSheep is the outcast obviously. I was also one of those :P My car also turned out to be Black, and not many people took it for a fast car, so it was a nice little outcast in itself.
It'* a full on take of everything, and has been my internet handle for almost 10 years now. So I just use that handle for anything I do.