Then, Smash Bros. must really drive you nuts. Imagine that game if you couldn't choose the same character in multiplayer. How can Mario fight himself? AHHH!
Actually, that was one thing that I didn't like about Melee. Not that you can pick the same character, that's fine and a must, but that there were selectable variations to the existing characters, notably Dr. Mario and Young Link. Something about that just... bothers me for some reason. I'm fine with Toon Link, as it's not actually the same character at a different point in time, and I'm not sure why I'm bugged by the multiple version thing but I am. It just seems taboo for some reason.
So yeah, I would have been happy had the babies not been in Mario Kart at all, and there are still enough characters to choose from where they don't need to resort to using them IMO (Dixie, Cackletta and the always ignored Koopa Kids).