Interestingly, in MegaMan X2 and X3, the Cx4 coprocessor built into the game cartridge is used for some very specific wireframe animations used in only very specific areas of each game and was largely unnecessary. (Only 2 scenes in X2: a miniboss and the final boss, and one scene in X3: after defeating the final boss)
Interesting, I had thought it did some sprite compression also but it looks like I was confusing it with the SDD-1. There's a lot of neat co-processors out there that got used. It's one of the things I loved about the cartridge era systems because it let them get upgraded in ways you can't do anymore.
