I was wondering how i could swap 2d characters in game or create a mutation type blueprint?

i am looking to implement a mutation type of aspect to a game that me and some class mates are doing for a project. we are looking to have 3 characters, a neutral character and a good and bad character, and be able to mutate from neutral to good and bad mutations, and the good and bad mutations to morph back to the neutral character. i think this is the easiest way to explain what i am looking for, or at least hope it is.