Excellent game!
Great fighting game, absolutely love it when a great idea comes off well.
Combat was fluid. Characters felt balanced and unique. Varying modes means that there's always something to do. The camera was the best dynamic (I.E., not following a preset path) camera I've seen in any Flash game. Graphics were crisp and well-drawn. My suggestion, however, is to give different appearances to multiple versions of the same character. When you and your opponent are the same character, identifying yourself in the heat of battle is next to impossible - an unavoidable difficulty in Survival mode. Perhaps a different tinting for each unique instance of each character? As in, a red-shirted Pico if another player is the original one.
Would like to point out a bug, though. I was in Survival mode. The enemy grabbed the 'giant' powerup, but I managed to kill him by knocking him off the edge (note: I'm not sure if I killed him with my attack, or if the fall dealt lethal damage). When the next enemy spawned in, he was still supersized - and the powerup didn't wear off. Luckily, killing this next, giant enemy caused the NEXT foe to revert to normal. Still, this was kinda strange.