My first game in the videogame business was for an arcade game. By that, I mean a big cabinet that eats quarters every 2 minutes. It was a 3D game, and I was in charge of some gameplay features; putting moves into the game. The process was intensive! We would come up with a series of moves we would like, then ask the animators to provide them, and a few days later we would have some animation files that made our 3D models perform those moves.
But remember: Good game development is iterative!
So of course we would always come up with some extra moves that we didn't think of initially. This is natural; we are always being influenced by TV, movies, sports, and pretty much anything with action. Sometimes we would ask for new animations and get them; but there eventually comes a time where there is no more time to get new animations. So I remember being tasked with looking through the old animations and piecing together new moves from the remnants of the old ones... and THAT was fun because it exercised my creative and technical sides; selecting interesting moves and figuring out how to put them together.
In our game, since it is 2D, the animations ARE the models. We achieve motion by flipping frames on a character like a traditional animation. There is no difference. But I am finding more and more that by looking through each frame, I can come up with entire new moves for the variations on the enemies. You'ld be surprised even by simply stringing old moves together or adjusting the playback speed you can get cool new supermoves.