Go to 1p mode, then pick time trials, then pick whoever you want to on any cart. Pick Sherbert Land (Star Cup) then go backward. Turn around. Go to the giant ice things and right when you are about to hit it switch (Z button). When you get unfrozen you should notice that on the map something is not right.(Lets say you were Mario and Luigi. Mario is on the back but on the map it says Luigi is on the back. To get them both on the back press Y or X. DONT SWITCH. You can still drive around but don't get hit by anything. YOU DONT HAVE TO DO TIME TRIALS OR 1P MODE. IT IS JUST THAT THERE IS A LESS LIKELY CHANCE THAT YOU WILL GET HIT

Have fun with this cheat.

You can get an easy mushroom by a shell( red or green).When you see a red car with white dots and shaped like a mushroom, hit it with a shell. It will pop out a mushroom. This way is more convenient than bumping your Kart into the car and slower your speed, and you can even get a mushroom by using a green shell when you're in 1st place.

Ok now this isn't the best cheat in the world or anything but it's pretty neat.On the level Peach Beach when you first get started keep going until the first turn,but do NOT go right!Turn left and you should see a green pipe.Go inside of it and you should get shot out and you will get a double box.
(NOTE)There are only four of these in the whole level so....START YOUR ENGINES!

If you want to be stable and not fall of the bridge on the donkey kong level near the finish post do this.If you are falling to the right of the bridge click the L button and if you fall to the left click the R button. Good Luck!!!!!

Beating the staff ghosts doesn't earn you anything, but it does give you something to brag about. If you beat the time, you will unlock the staff ghost. After the time is the driver/passenger "kart". I don't know the times it takes them to go around the track.

MUSHROOM CUP
Luigi Circuit: 1:29:000 Luigi/Mario "Red Fire"
Peach Beach: 1:18:000 Peach/Daisy "Bloom Coach"
Baby Park: 1:13:000 Baby Mario/Baby Luigi "Mario Buggy"
Dry Dry Desert: 1:52:000 Birdo/Yoshi "Turbo Yoshi"

FLOWER CUP
Mushroom Bridge: 1:31:000 Koopa/Paratroopa "Koopa Wing"
Mario Circuit: 1:42:000 Mario/Luigi "Red Fire"
Daisy Cruiser: 1:51:000 Daisy/Peach "Peach Coach"
Waluigi Stadium: 2:00:000 Waluigi/Wario "Wario's Jalopy"

STAR CUP
Sherbet Land: 1:26:000 Baby Luigi/Baby Mario "Mario Buggy"
Mushroom City 1:51:000 Paratroopa/Koopa "Para Wing"
Yoshi Circuit: 2:02:000 Yoshi/Birdo "Turbo Yoshi"
DK Mountain: 2:10:000 DK/Diddy "DK's Kart"

SPECIAL CUP
Wario Coliseum: 2:23:000 Wario/Waluigi "Wario's Jalopy"
Dino Dino Jungle: 2:03:000 Diddy/DK "DK's Kart"
Bowser's Castle: 2:46:000 Bowser/Bowser Jr. "Bowser's Kart"
Rainbow Road: 3:19:000 Mario/Peach "Red Fire"

Hello. I am marthman. I am new to this so this is my first cheat.

On any turn if you hold L and R trn left/right while wigling the control stick left and right. Do that and then red sparks shoul come up then blue sparks come up. Let go and you get a small booost it works trust ME

All Cup Tour
Special Cup - 150cc - Gold

Mirror Mode
All Cup Tour Cup - 150cc - Gold

Green Fire - Luigi's Kart
Mushroom Cup - 50cc - Gold

Bloom Coach - Daisy's Kart
Flower Cup - 50cc - Gold

Para Wing - Paratroopa's Kart
Star Cup - 50cc - Gold

Bullet Blaster - Bowser Jr's Kart
Special Cup - 50cc - Gold

Battle Buggy - Baby Luigi's Kart
Mushroom Cup - 100cc - Gold

Waluigi Racer - Waluigi's Kart
Flower Cup - 100cc - Gold

Toad and Toadette
Unlock one of their karts

Toad's Kart - Toad's Kart
Special Cup - 100cc - Gold

Luigi's Mansion Battle Stage - 2p Only
Mushroom Cup - 150cc - Gold

Turbo Birdo - Birdo's Kart
Flower Cup - 150cc - Gold

Barrel Train - Diddy Kong's Kart
Star Cup - 150cc - Gold

Petey Pirahna and King Boo
Unlock one of their karts

Toadette's Kart - Toadette's Kart
Mushroom Cup - Mirror Mode - Gold

Tilt-A-Kart Battle Stage - 2p Only
Flower Cup - Mirror Mode - Gold

Pirahna Pipes - Petey Pirahna's Kart
Star Cup - Mirror Mode - Gold

Pipes Kart - King Boo's Kart
Special Cup - Mirror Mode - Gold

Toadsworth's Kart - Toadsworth's Kart
All Cup Tour Cup - Mirror Mode - Gold

Parade Kart - No-one's Kart
All Cup Tour Cup - Mirror Mode - Gold

Press L, R, Y, A at the main screen(title screen)

Bowser first then King boo on boo pipes or parde kart. Or King boo first with mario.

If you beat all the cups in 50cc through 150cc you will recieve the Mirrior Course.

You will recieve these if you beat the Mushroom, Flower, Star, Special, All Cup Tour Cups:

Mushroom Cup:
Toadette Kart

Flower Cup:
Tilt
(I don't know what the name was but it is a battle mode stage)

Star Cup:
Petey Piranah & King Boo With Piranah Pipes

Special Cup:
Boo Pipes

All Cup Tour:
Parade Kart

To get better times in time trial mode use mini boosts ALL THE TIME!

Beat all cup tour on 150cc.

Mini boost: On any turn, drift (hold L or R while turning) now, using the control stick, and still holding L or R, go left to right the sparks turn red.

Now go left right again the sparks turn blue.

Release L or R. youl get a small but fast speed boost....

To get a boost at the start of the race tap the A button when the 3 2 1 is counting down.