Leaders:
Kim Possible (Kim Possible)
Danny Fenton (Danny Phantom)
Aang (Avatar: The Last Airbender)
Garnet (Steven Universe)
Tulip Olsen (Infinity Train)
Starring:
Gertie the Dinosaur (1914 Wener Herzog cartoon of the same name)
Felix the Cat (Felix the Cat)
Mickey Mouse, Donald Duck, Goofy, Pluto, Pete (Mickey Mouse)
Bugs Bunny, Daffy Duck, Porky Pig, Elmer Fudd, Tasmanian Devil, Sylvester the Cat, Wile E. Coyote and the Road Runner, Dan Backslide (Looney Tunes)
Tom (Tom and Jerry)
Huckleberry Hound (The Huckleberry Hound Show)
Rocky and Bullwinkle (Rocky and Bullwinkle)
Fred Flintstone (The Flintstones)
Yogi Bear (The Yogi Bear Show)
George Jetson (The Jetsons)
Pink Panther (The Pink Panther)
Underdog (Underdog)
Charlie Brown, Snoopy and Woodstock (Peanuts)
Speed Racer (Speed Racer)
Dick Dastardly and Muttley (Wacky Races)
Scooby Doo, Shaggy, Fred, Velma, and Daphne, Scrappy Doo, Vincent van Goul (from 13 Ghosts) (Scooby Doo)
Fat Albert (Fat Albert and the Cosby Kids)
Grape Ape (The Great Grape Ape Show)
Dynomutt and Blue Falcon (the latter is Brian in Scoob!) (Dynomutt: Dog Wonder)
Mumbly and Dread Baron (Laff-a-Lympics)
Various different species of Smurfs (mostly Papa Smurf and Smurefette) and Gargamel (The Smurfs)
He-Man / Prince Adam, Teela, Man-at-Arms, Orko, the Sorceress, Skeletor, Evil-Lyn, and Beast Man (He-Man and the Masters of the Universe)
Inspector Gadget, Penny, Brain, and Dr. Claw (Inspector Gadget)
Optimus Prime (The Transformers)
Thomas (Thomas the Tank Engine)
Lion-O (ThunderCats)
Leonardo, Michelangelo, Raphael, Donatello, Splinter, April, Shredder, Bebop, and Rocksteady (Teenage Mutant Ninja Turtles) (role from 2012 cartoon)
Scrooge McDuck, Huey, Dewey, and Louie, Webby Vanderquack, Launchpad (DuckTales) (role from 2017 reboot)
Garfield (Garfield and Friends)
Winnie the Pooh, Tigger, Piglet, and Eeyore (Winnie the Pooh) (has nothing to do with Pooh's Adventures by the way)
Homer, Bart, Lisa, Marge, Sideshow Bob, Mr. Burns, and Principal Skinner (The Simpsons)
Wallace and Gromit (Wallace and Gromit)
Baloo (TaleSpin)
Captain Planet (Captain Planet) (since he did have a surprise appearance in Punch Time Explosion and appeared in an OK K.O. episode)
Doug Funnie (Doug)
Ren Hoek and Stimpy Cat (Ren and Stimpy)
Tommy Pickles, Chuckie Finster, and Angelica Pickles (Rugrats)
Darkwing Duck (Darkwing Duck)
AEon Flux (AEon Flux)
Batman (Batman: The Animated Series)
Yakko, Wakko, and Dot Warner, Dr. Scratchensniff, Pinky and the Brain (Animaniacs / Pinky and the Brain)
Sonic the Hedgehog, Tails, Sally Acorn, Dr. Robotnik, Scratch and Grounder (Sonic the Hedgehog (Sat AM) and Adventures of Sonic the Hedgehog)
Beavis and Butt-Head (Beavis and Butt-Head)
Spider-Man (Spider-Man: The Animated Series)
Tick (The Tick)
Space Ghost, Zorak, Moltar, and Brak (Space Ghost Coast to Coast)
Ms. Frizzle and Arnold Perlstein (The Magic School Bus)
Freakazoid (Freakazoid!)
Dexter, Dee Dee, Mandark, Monkey, Major Glory, Valhallen, and the Krunk (Dexter's Laboratory)
Arnold, Gerald, and Helga (Hey, Arnold!)
Superman (Superman: The Animated Series)
Eric Cartman, Kyle Broflovski, Stan Marsh, and Kenny McCormick (South Park)
Johnny Bravo (Johnny Bravo)
Hank Hill, Bobby Hill, Dale Gribble (King of the Hill)
Daria Morgenderffer (Daria)
Blossom, Bubbles, Buttercup, Professor Utonium, Mojo Jojo, Him, Princess Morbucks, and Fuzzy Lumpkins (The Powerpuff Girls)
SpongeBob SquarePants, Patrick Star, Squidward Tentacles, Sandy Cheeks, Mr. Krabs, Plankton (SpongeBob SquarePants)
Peter, Stewie, Lois, Chris, Meg, and Brian Griffin, Joe, Cleveland, Quagmire, and Ernie the Chicken (Family Guy)
Ed, Double D, and Eddy (Ed, Edd, 'n Eddy)
Courage, Eustace Bagge, Katz (Courage the Cowardly Dog)
Dora, Boots, and Swiper (Dora the Explorer)
Harvey Birdman (Harvey Birdman: Attorney at Law)
Timmy Turner, Cosmo and Wanda, Vicky, Mr. Crocker (The Fairly OddParents)
Zim (Invader Zim)
Jack, Aku (Samurai Jack)
Grim Reaper, Billy and Mandy, Hoss Delgado (The Grim Adventures of Billy and Mandy)
2D, Murdock, Noodle, Russel Hobbs, Ace (Gorillaz)
Jimmy Neutron, Carl Wheezer, Sheen Estevez, Cindy Vortex (The Adventures of Jimmy Neutron: Boy Genius)
Abe Lincoln, Gandhi, Joan of Arc, JFK, Cleopatra (Clone High)
Kim Possible, Ron Stoppable and Rufus, Dr. Drakken, Shego (Kim Possible)
Numbuh 1-5, Father, Toiletnator (Codename: Kids Next Door)
Robin, Starfire, Cyborg, Beast Boy, Raven (Teen Titans) (No, I'm not using the 2013 reboot because it sucks)
Jenny Wakeman (My Life as a Teenage Robot)
Mac and Bloo, Wilt, Eduardo, Cheese, Frankie (Foster's Home for Imaginary Friends)
Danny Fenton (Danny Phantom)
Ami and Yumi (Hi Hi Puffy AmiYumi)
Aang (Avatar: The Last Airbender)
Ben Tennyson (Ben 10) (the original 2005 series to be exact)
Stan Smith, Roger Smith (American Dad!)
Lazlo (Camp Lazlo)
The Chicken (Robot Chicken)
Juniper Lee (The Life and Times of Juniper Lee)
Jake Long (American Dragon: Jake Long)
Curious George, the Man With the Yellow Hat (Curious George)
Phineas and Ferb, Candace Flynn, Dr. Doofenshmirtz, Perry the Platypus, Isabella, Buford, Baljeet (Phineas and Ferb)
Chowder (Chowder)
Flapjack, Captain K'nuckles (The Marvelous Misadventures of Flapjack)
Chris McLean, Chef Hatchet, the original 22 campers from Island, Devin and Carrie (Total Drama)
Finn the Human, Jake the Dog, Princess Bubblegum, Ice King, Marceline (Adventure Time)
Mordecai, Rigby, Benson, Skips, Muscle Man (Regular Show)
Gumball Watterson, Darwin Watterson (The Amazing World of Gumball)
Bob Belcher, Louise Belcher (Bob's Burgers)
Dipper and Mabel Pines, Grunkle Stan, Soos, Wendy Corduroy, Bill Cipher, Pacifica Northwest (Gravity Falls)
Korra (The Legend of Korra)
Rick Sanchez and Morty Smith (Rick and Morty)
Steven Universe, Garnet, Amethyst, Pearl, Connie Mahaswaren, Greg, Peridot, Lapis Lazuli, Jasper (Steven Universe)
Star Butterfly, Marco Diaz (Star vs. the Forces of Evil)
Ladybug, Cat Noir (Miraculous Ladybug)
Lincoln, Lori, Leni, Luna, Luan, Lynn, Lucy, Lana, Lola, and Lisa Loud, Ronnie Anne (The Loud House / The Casagrandes)
K.O., Enid, Radicles, Strike (the latter from the episode "Crossover Nexus" and the main villain of the series) (OK K.O.! Let's Be Heroes)
Tulip Olsen (Infinity Train)