I'll just be using one character.
Nick: A creature made from combining Fox DNA with Chaos and Majin mass. Though I usually look solid I am actually a blob, and can switch at any time to attack by stretching, altering my form, or engulfing the opponent. I can also eat enemies, keep them in my stomach a turn, then spit them back out and learn their moves for the rest of the fight. I can't use the Chaos Emeralds the normal way, but if I eat them I become a lot bigger and more powerful. I'm a mean little brat and love to taunt and insult people and if you make me mad I'll eat you, but if someone manages to get on my good side I can be a lot nicer.