NOTE: it's called Rainbow Road. First, you must go to any Grand Prix mode. After choosing your character and kart or bike, choose the flower cup. Finish it. You will unlock the star cup. Complete that, and you'll get the special cup. Rainbow Road is in that cup.
You have to get Mario Galaxy and then you will unlock her or get at least one star on all 150cc Mirror races and you will unlock her.
Unlock the star cup and play it.
Eheh...it's already there. Check the last race of the Special Cup...
50cc star cup
To unlock the quaker you have to win 150cc star cup
You can't, he's not in Mario Kart DS. However, you can get him in Mario Kart Wii, Mario Kart 7, and Mario Kart 8, and Mario Kart 8 Deluxe.
You unlock star cup by by winning any cup in the flower cup in the respective class you want to unlock.
Win the 50cc Star Cup.
either get high star ranks or get high medals.
(medium): Win the Mirror Star Cup.
Get Star Rank In The Top Cups.
You have to do the Flower Cup, and the Mushroom Cup.