Literally Everything Kart

Starter (Lvl. 1)

 * Batman
 * Darth Vader
 * Forrest Gump
 * The Joker
 * Mario

Lvl. 2

 * Bugs Bunny
 * Dora The Explorer
 * Indiana Jones
 * Jar Jar Binks
 * Spider-Man

Lvl. 3

 * Bubsy
 * Caillou
 * Dr. Manhattan
 * Goku
 * Iron Man

Lvl. 4

 * Miles "Tails" Prower
 * Pikachu
 * Silver Surfer
 * SpongeBob SquarePants
 * Superman

Lvl. 5

 * Angelica Pickles
 * Bubbles (PPG)
 * Chuck E. Cheese
 * Sonic the Hedgehog
 * Wolverine

Lvl. 6

 * Arthur Read
 * Barney The Dinosaur
 * Captain America
 * Diego (Go Diego Go)
 * Shazam

Lvl. 7

 * The Flash
 * Green Lantern
 * Hulk
 * Sentry
 * Thor

Lvl. 8

 * Jean Grey
 * Luigi
 * Mickey Mouse
 * Peach
 * Wario

Lvl. 9

 * Bowser
 * Charlie Brown
 * Larry Koopa
 * Morton Koopa Jr.
 * Waluigi

Lvl. 10

 * Bowser Jr.
 * Daisy (Mickey Mouse)
 * Daisy (Super Mario)
 * Scrooge McDuck
 * Tommy Pickles

Mario Star Cup

 * SNES Mario Circuit 1
 * N64 Mario Raceway
 * GBA Mario Circuit
 * GCN Mario Circuit

Luigi's Cup

 * N64 Luigi Raceway
 * GBA Luigi Circuit
 * GCN Luigi Circuit
 * DS Luigi's Mansion

Super Wario Cup

 * N64 Wario Stadium
 * GCN Wario Colosseum
 * DS Wario Stadium
 * Wii Wario's Gold Mine

Waluigi Tires Cup

 * GCN Waluigi Stadium
 * DS Waluigi Pinball
 * WaluigiWare, LLC.
 * Waluigi's Taco Stand

Bowser Oil Cup

 * SNES Bowser Castle 1
 * N64 Bowser's Castle
 * GBA Bowser Castle 1
 * GCN Bowser's Castle

Piston Cup

 * Motor Speedway of the South
 * Los Angeles International Raceway
 * Radiator Springs Motor Circuit
 * Tractor Field