Here are some of the Mario Kart Wii’s Easter Eggs and Unlockables as submitted by some of its users. Feel free to add more in the comments section of this post.

Golden Wii Wheel

Use the Wii Wheel a whole bunch in all modes, and when you go online a golden Wii Wheel will be next to your name.

Golden Stars

If you get a 1 star rank on all races in all cups, you’ll get a star next to your name when playing online. If u have 2 star rank in every race on every cup, you’ll have 2 stars next to your name and you’ll get a third star with 3.

Unlockable Characters

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 Races

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

Unlockable Vehicles

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
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