Marvel vs. Capcom has a pretty sizable list of characters that you direct to pummel each other for no real reason. There are representatives from both the Marvel and Capcom universes here, but there are even more characters on the roster that you can get to, though you have to go through a bit of a rigmarole to get at them.

So, what happens, for instance, if you start your cursor on Zangief

Then move your joystick Left, Left, Down, Down, Right, Right, Down, Down, Left, Left, Up, Right, Up, Up, Right, Right?

Why, your cursor would go off the side of the roster and you'd have Roll selected. Roll, as you may or may not know, is the 'sister' of Mega Man.

Roll controls a lot like Mega Man, but she's small, weak, and kind of slow. So, why would you want to choose her?

Because beating someone by using an underpowered character is pretty embarrassing. For the guy you beat, of course. But that's going to take a lot of practice.