Cool surprise characters

In games based on comics, movies etc., what are examples of some cool minor character making unexpected appearance?
(LEGO games don't count since they have ALL possible characters...)


In PC version of Spider-Man 2 (generally much worse, completely different game than the console versions), there is Puma. Apparently the character has only ever appeared in this game and the GBA version of the same.
I have great personal nostalgia as the very first Spider-Man comic - in fact any Marvel comic - I ever read had him. It was the next issue after his first appearance. So it was really cool to see (and fight) him.