OK, so we all are nagging that we want different characters, courses, stages and bikes and karts and modes. So we can all discuss our wish lists here. I mostly care about the characters in this case, so here's what I think the UNLOCKABLES should be in:

Paper Mario
Paper Peach
Baby Wario
Baby Waluigi
Goomba
Hammer Bro
Blooper
Ms Mowz
Pianta
Paper Luigi
Cranky Kong
Tiny Kong
Dixie Kong
Goombella
Koops
Flurrie
Vivian
Bobbery

What else?

I definitely agree with the Baby Wario and Waluigi choices!!!! but i would add Shy guy or Monty Mole. Also Count Bleck would be EPIC!!!!

how about shy guy?

Definatley Goomba!

how bout characters from other games eg.sonic samus link and ike

No, it would kill the game.
It'd go from mario kart, to nintendo kart.

R.O.B he has to return

Yeah r.o.b. bak in! And eh how is paper mario and paper luigi meant to drive i mean they are paper...

I mean having Paper characters would be good since they could use the stars as there special item. I definitley think there should be a different circuit than Grumble Volcano, I like it, but it's like the others. The same old thing. I think they should do one like a rollercoaster.

Shy Guy and Monty Mole. THOSE 2 FTW!!!!