Mario Kart Wii Cheat Codes

The Mario Kart Wii Cheat Codes have already been released!

Courses
Unlockable How to Unlock
Star Cup Win at least 3rd place in Flower Cup and Mushroom Cup
Special Cup Win at least 3rd place in Star Cup
Leaf Cup Win at least 3rd place in Banana Cup and Shell Cup
Lightning Cup Win at least 3rd place in Leaf Cup
Mirror mode
Win all cups at 150cc class.

Characters
Unlockable How to Unlock
King Boo Win 50cc Star Cup
Diddy Kong Complete retro 50cc Cups
Baby Daisy 1 Star in all 50cc Wii-Cups
Dry Bones Win 100cc Leaf Cup
Mii (Outfit A) Win 100cc Special Cup
Bowser Jr. 1 Star in all 100cc Retro-Cups
Daisy Win 150cc Special Cup
Dry Bowser 1 Star in all 150cc Wii-Cups
Rosalina Have a Super Mario Galaxy savefile and she will be unlocked after 50 races or get 1 star in all Mirror Mode Retro-Cups
Funky Kong Unlock 4 Expert Staff Ghost Data in Time Trials
Baby Luigi Unlock 8 Expert Staff Ghost Data in Time Trials
Birdo Play Time Trials on 16 different courses or win 250 Wi-Fi matches.
Toadette Play Time Trials on all 32 different courses or win 1000 Wi-Fi matches.
Mii (Outfit B) Unlock all 32 Expert Staff Ghost Data in Time Trials

Unlockable Karts
After meeting the requirements, some unlockables may require you to back out of your save file and reselect it.


Unlockable How to Unlock:
Aero Glider (large kart) Attain at least 1 Star in all 150cc Retro Cups
B Dasher Mk 2 (Medium Kart) Unlocked 24 Expert Staff Ghosts
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
Tiny Titan (small kart) Beat 50 opponents during Wi-Fi play

Unlockable Bikes
After meeting the requirements, some unlockables may require you to back out of your save file and reselect it.

Unlockable How to Unlock
Quacker (small bike) Win 150cc Star Cup
Bubble Bike (small bike) Win Mirror Leaf Cup
Magikruiser (small bike) Play Time Trials on 8 different courses
Rapide (medium bike) Win 100cc Lightning Cup
Nitrocycle (medium bike) Attain at least 1 Star Rank for all 100cc Wii Grand Prix Cups
Dolphin Dasher (medium bike) Win Mirror Star Cup
Twinkle Star (large bike) Win 100cc Star Cup
Phantom (large bike) Win Mirror Special Cup
Torpedo (large bike) Unlock 12 Expert Staff Ghost Data in Time Trials
Alternate Title Screen and Ending Screen
Completing every single cup with a first place unlocks two new alternating Title Screens and one new Ending Photo.
Have a star by your nickname
Playing extraordinarily well in Grand Prix races can produce a Star Ranking upto 3 at the end results instead of the standard "C, B or A."

Collecting these stars in all Grand Prix's adds a Star Icon next to your name in WiFi Races and on the Results Screen for your opponents to see.

(Note: Say, if you get a Three star rating in every Grand Prix except one which you got a One star rating in. You would get a One starred nickname until you manage to upgrade the rank.)

Unlockable How to Unlock:
One starred nickname Get a one star rating in every Grand Prix
Double starred nickname Get a two star rating in every Grand Prix
Triple starred nickname Get a three star rating in every Grand Prix.
Golden Wii Wheel
Use the wii wheel extensively in all the modes, when you go online a golden wii wheel will be next to your name.

Mario Kart Wii Secrets

Quick Start
When the countdown starts wait till the 2 starts to disappear and then press and hold the 2 button. So the 2 must still be visible but disappearing.
This will give you a boost at the start of the race.
Boost when recovering from a fall
When you fall into something, such as water or falling from rainbow road, when you land, if you hit 2 at the moment you hit the ground, you get a temporary boost.

Mario Kart Wii Glitches
More than one person can be the same character.
First, make P1 choose the character you both want to be. Then unselect the character and move off of it. Move P2 over, and select the character. Go back one screen, then go into the character select again. You should both be on the same character. Both of you select the character. Do whatever you want from there on.

Note: In the character select screen and options, whenever one of you does an animation, both of you will. Also, if P2 chooses a different kind of vehicle than P1, P1 will look strange. Don't worry, this won't actually happen in the game.

I haven't tested this with P3 or P4 yet, but in theory, it should work.

source: gamespot

Enjoy your Mario Kart Wii Cheat Codes!