Same-Type Mutation is an alternative game type used in Super Smash Bros. Battle Cards. In this game type, a Basic Smasher can evolve into any Stage 1 Smashers that are the same type as the Basic Smasher. The same applies when evolving into Stage 2 Smashers. Evolution in this game type allows you to ignore the character specific type when evolving, as well as putting FS cards onto Smashers. (If a Smasher FS is of a Stage 2 Smasher, it still can only be put on top of a Stage 2 Smasher.)
The only rule the players must follow when evolving Smasher, is that the evolved Smasher card must be the same Energy-type as the Smasher that card is being played on top of. For Evolved Smashers with multiple Energy-types, the previous Smasher's Energy-type only has to match 1 of the Evolved Smasher's Energy-types in order to evolve into that Smasher. The Smasher can still evolve into Smashers of different Energy-types if they could still normally evolve into that Smasher. This game type is compatible with any other of the game types used in Super Smash Bros. Battle Cards.