Mario Kart Wii/Characters

The weight of each character has little effect in and of itself, but will affect the types of vehicle available to the player.

Lightweight

 * Toad
 * Koopa Troopa
 * Baby Mario
 * Baby Peach

Middleweight

 * Mario
 * Luigi
 * Peach
 * Yoshi

Heavyweight

 * Wario
 * Donkey Kong
 * Bowser
 * Waluigi

Unlockables
Note: In order to unlock characters via Time Trials, you must also restart the game in order for it to take effect.

Lightweight

 * Baby Luigi
 * Unlock 8 Expert Staff Ghost Data on Time Trials.


 * Baby Daisy
 * Attain at least 1 Star Rank for all 50cc Nitro Grand Prix Cups.


 * Dry Bones
 * Attain a Gold Trophy in the 100cc Leaf Cup.


 * Toadette
 * Play on all 32 courses in Time Trials.

Middleweight

 * Daisy
 * Attain a Gold Trophy in 150cc Special Cup.


 * Diddy Kong
 * Attain Gold Trophies in all 50cc Cups.


 * Birdo
 * Beat 250 people while playing online, or
 * Play on 16 courses in Time Trials.


 * Bowser Jr.
 * Attain at least 1 Star Rank for all 100cc Retro Cups.

Heavyweight

 * King Boo
 * Attain a Gold Trophy in 50cc Star Cup.


 * Rosalina
 * With a Super Mario Galaxy save on your Wii, she will appear randomly in game. This can range from just starting the game up, by collecting trophies with Starred Ranks in Grand Prix Mode, or by unlocking Fast Staff Ghosts in Time Trials Mode.


 * Funky Kong
 * Unlock 4 Fast Staff Ghost Data in Time Trials.


 * Dry Bowser
 * Attain at least a 1-Star Rank in all 150cc Nitro Grand Prix Cups.

Miscellaneous

 * Mii (Outfit A)
 * Attain a Gold Trophy at 100cc Special Cup.


 * Mii (Outfit B)
 * Unlock all Expert Staff Ghost Data in Time Trials.