Nicktoons Racing is a Nickelodeon racing game for the PlayStation, Game Boy Advance, Game Boy Color, Windows, and arcade.
Tommy Pickles: A small baby with a big heart who loves to have adventures with his friends. Drives the Reptar Wagon.
Angelica Pickles: Tommy's bratty cousin who loves to make fun of Tommy and his friends. Drives her pink Cynthia car.
From Hey Arnold!:
Arnold: A bold football-headed kid who tries to solve the problems of every day life. Drives a cardboard soapbox kart.
Helga Pataki: A girl who picks on Arnold, but is secretly in love with him. Like Arnold, she drives a cardboard soapbox kart.
From The Wild Thornberrys:
Eliza Thornberry: A girl with the ability to talk to animals. Drives a miniature version of her family's Comvee.
Darwin: A chimp who is Eliza's best friend. Drives a Jungle Jeep.
Cat: A feline who enjoys relaxing, but doesn't get much of it with his brother Dog around.
Dog: A playful mutt who loves to play and usually causes problems.
From The Angry Beavers:
Norbert and Daggett: Two hip and happenin' beaver brothers. They drive together in a little log, but in the GBC version, they drive separate and their names are labeled vice versa.
From Aaahh!!! Real Monsters:
Ickis: A cowardly, rabbit-eared monster with the great ability of looming. Drives a beetle-shaped car. He doesn't appear in the GBC version.
From The Ren and Stimpy Show:
Stimpy: A stupid feline with a passion for Gritty Kitty, pre-chewed gum and his pal, Ren Hoek. Drives a litter box. He also doesn't appear in the GBC version.
From SpongeBob SquarePants:
SpongeBob SquarePants: A loyal sea sponge who loves his job at the Krusty Krab and his pet snail, Gary. Drives a car that resembles his pineapple house.
Patrick Star: SpongeBob's loyal, yet lazy starfish friend. Drives a boat.
Mystery Rider: A racer who, in the end, turns out to be Sheldon J. Plankton. He always tries to think of ways to steal the Krabby Patty Secret Formula. The reason he enters the race is so he can win the year supply of Krabby Patties. He is an unlockable character.
Source: Wikipedia, "Nicktoons Racing", available under the CC-BY-SA License.