Mario Kart Wii Cheats

Shockwave
When you see the POW block coming, flick the remote/wheel to make a shockwave that makes you immune to it. You will stay at the same speed, but you will lose the items you are holding.
Different Mii Classes
When you play as your Mii, you have a certain weight class. You can change your weight in the Mii channel, and get different cars.
Falling Boost
When you fall, for example, into a pit, press 2 the moment you hit the ground for a speed boost.
Starting Boost
When you are starting, as soon as you see the 2 just about disappear, press and hold 2 for a speed boost.
Nickname Stars
Unlockable
How to Unlock
Double starred nickname
Get a two star rating in every Grand Prix
One starred nickname
Get a one star rating in every Grand Prix
Triple starred nickname
Get a three star rating in every Grand Prix

Unlockable Characters
Unlockable
How to Unlock
Baby Daisy
1 Star in all 50cc Wii-Cups
Baby Luigi
Unlock 8 Expert Staff Ghost Data in Time Trials
Birdo
Play Time Trials on 16 different courses
Bowser Jr.
1 Star in all 100cc Retro-Cups
Daisy
Win 150cc Special Cup
Diddy Kong
Complete all 50cc Cups
Dry Bones
Win 100cc Leaf Cup
Dry Bowser
1 Star in all 150cc Wii-Cups
Funky Kong
Unlock 4 Expert Staff Ghost Data in Time Trials
King Boo
Win 50cc Star Cup
Mii (Outfit A)
Win 100cc Special Cup
Rosalina
Have a Super Mario Galaxy savefile and she will be unlocked after some GPs
Toadette
Play Time Trials on all 32 different courses
Unlockable Courses
Unlockable
How to Unlock
Leaf Cup
Win at least 3rd place in Banana Cup
Lightning Cup
Win at least 3rd place in Leaf Cup
Special Cup
Win at least 3rd place in Star Cup
Star Cup
Win at least 3rd place in Flower Cup
Mirror Mode
Win all cups at 150cc class.
Unlockable Bikes
Unlockable
How to Unlock
Bubble Bike (small bike)
Win Mirror Leaf Cup
Dolphin Dasher (medium bike)
Win Mirror Star Cup
Magikruiser (small bike)
Play Time Trials on 8 different courses
Nitrocycle (medium bike)
Attain at least 1 Star Rank for all 100cc Wii Grand Prix Cups
Phantom (large bike)
Win Mirror Special Cup
Quacker (small bike)
Win 150cc Star Cup
Rapide (medium bike)
Win 100cc Lightning Cup
Torpedo (large bike)
Unlock 12 Expert Staff Ghost Data in Time Trials
Twinkle Star (large bike)
Win 100cc Star Cup
Unlockable Karts
Unlockable
How to Unlock
Blue Falcon (small kart)
Win Mirror Lightning Cup
Cheep Charger (small kart)
Attain at least 1 Star Rank for all 50cc Retro Grand Prix Cups
Dragonetti (large kart)
Win 150cc Lightning Cup
Piranha Prowler (large kart)
Win 50cc Special Cup
Rally Romper (small kart)
Unlock 1 Expert Staff Ghost Data in Time Trials
Royal Racer (medium kart)
Win 150cc Leaf Cup
Turbo Blooper (medium kart)
Win 50cc Leaf Cup