I gotta say that every character is extremely unique. An that is something that can't be said for many other fighters today. Every character in KI plays vastly different than other characters in the cast. I think that Rash is a great fit to the game, although I do agree that I've never seen the appeal to Battletoads either. By the looks of the trailer and what is currently available there are some moves that are yet to be released for the first month of play with the character. Which is a known thing that the character is still under development. But to be honest, you have an ice alien, a fire man, a babylonian sorcerer, a GIANT golem, I don't see how an alien/mutant toad creature doesn't. He is admittedly VERY cartoony, but he is a guest character. He doesn't break the game or break the style of what is already presented to us, and has everything that every other character has in the way of combat traits and unique mechanic.
