The actual game is called mugen (or m.u.g.e.n.). The game pretty much consist of ripped or hanfmadecharacters from other games fighting it out similar to a street fighter type game. Though I have heard of them ugen engine being used to make overhead games and other types of side scrollers (like final fight).
If you want 2d final fight/double dragon type of games then check out beats of rage and its zilion mods (
www.lavalit.com)
ok I just checked on google, yup I was right it was some characters they added to one of the mugen games. I found the character (peter griffin), but its easier to just find the mod and dl the whole thing