To PMJ: I get the feeling that this game was originally going to be like Double Dash!! and have two characters to a Kart. In fact, if you look at the full character roster, they all seem to line up horizontally in pairs with the exception of the Kongs and the Bowsers, who are in vertical arrangements of threes. Baby Mario gets paired with Baby Luigi; likewise, Baby Peach would need a counterpart, so they put in Baby Daisy. There's also no other reason for Toadette to return except to pair up with Toad, considering that she was missing in Mario Kart DS. (I would've preferred Toadsworth though.) This is also assuming King Boo would be paired up with Rosalina as featured characters in console Mario games.
About myself: I think I'm done purposely lowering my online rankings. I'm at about 2630, I think. Now I'm going to climb back up to see what happens. Beware if you see a TJefferson. (I couldn't get the right kind of hair for him, unfortunately.)