In Mario Kart: Double Dash!! 
you can unlock new karts, characters 
and modes by getting gold in the trophies 
of the Grand Prix mode! Here is a list of 
what the cc of the kart is, the cup, 
and what is unlocked.

50cc

Mushroom Cup - Green Fire (Kart)
Flower Cup -   Bloom Coach (Kart)
Star Cup -     Para Wing (Kart)
Special Cup -  Bullet Blaster (Kart)
All Cup Tour - Nothing

100cc

Mushroom Cup - Rattle Buggy (Kart)
Flower Cup -   Wuluigi Race (Kart)
Star Cup -     Special Cup
Special Cup -  Toad & Toadette (Characters), 
Toad Kart (Kart)
All Cup Tour - Nothing

150cc

Mushroom Cup - Luigi's Mansion (Battle Mode Stage)
Flower Cup -   Turbo Birdo (Kart)
Star Cup -     Barrel Train (Kart)
Special Cup -  All Cup Tour (Grand Prix Mode)
All Cup Tour - Mirror Mode (Engine Options)

Mirror

Mushroom Cup - Toadette Kart (Kart)
Flower Cup -   Tilt-a-Kart (Battle Mode Stage)
Star Cup -     Petey Piranha & King Boo (Characters), 
Piranha Pipes (Kart)
Special Cup -  Boo Pipes (Kart)
All Cup Tour - Parade Kart (Kart)


If you win gold in all the trophies, 
then you receive an alternative "Thanks
for Playing" Screen and an alternative 
Start Screen for your efforts!