His name is R.O.B he is a playable character. Like it or not - he is an important part of Nintendo's history. He was a machine during the NES that could put in your disk, and was active in some games. He is likely to be in MKWII too (48 characters, he should be one) so you better get used to him.
http://www.vgchartz.com/games/userreviewdisp.php?id=261
That is VGChartz LONGEST review. And it's NOT Cute Kitten DS