A former alien invader desperately looking for a purpose in life. His life is shattered when his home is destroyed by the Heartless, and he finds himself in possession of a peculiar weapon called the Keyblade. As a hero chosen to battle the forces of evil, Zim embarks on a quest to reunite his friends and save all other worlds from suffering the same fate as his own. The story's equivalent of Sora.
- The Atoner: He became this during the backstory.
- Catchphrase: "Shazbot."
- Chaotic Good
- Large Ham: Not even being an atoner keeps him from being this.
The fiery-tempered Head Wizard of the Royal Magi in the Comic Kingdom. Calvin was sent to find and follow the Keyblade bearer. He joins up with Zim to help him save the worlds. The story's equivalent of Donald.
- Drop the Hammer: His main weapon, with alchemical runes on it to give his attacks elemental properties.
- Gadgeteer Genius
- Troll: The precise reason Garfield keeps him around.
The Captain of the Royal Order of Crusaders in the Comic Kingdom, Hobbes was sent to find and follow the Keyblade bearer. He joins up with Zim to help him save the worlds. The story's equivalent of Goofy.
- Battle Trophy: He wears many necklaces decorated with teeth of the monsters he's killed.
- Body Paint: He has tribal tattoos all over his body.
- Flash Step
- Informed Attractiveness: While he retains his kitten-ish appearance, he's also considered handsome by his tribe's standards.
- Super Strength: He's able to stop a rampaging Eduardo by digging his feet into the ground and lifting him up into the air. He can also push the Guard Armor back when the latter attempts to squash him with its fist.
- Vague Age: Not even he knows his own age, only that he's around Calvin's age (12), thirteen at most.
- What Would X Do?: Another of his necklaces has a small plate that says "WWAD?" ("What Would Aslan Do?")
A floating, talking skull who travels with Zim and co. to keep a record of their adventures. The story's equivalent of Jiminy.
- Ascended Extra: He gets just as much screentime as Calvin and Hobbes, making him MUCH more prominent than Jiminy ever was.
Tropes involving multiple members of the group:
- Canon Foreigner: Gaz and Minimoose, who don't have Kingdom Hearts equivalents. While it's inevitable that a written adaptation would have more characters, they still count as canon foreigners because the group as a whole is equivalent to the trio of Sora, Riku, and Kairi. What role either of them will have remains to be seen.
- True Companions: All with Zim.
Zim's rival. His pursuit of all things paranormal leads to him being seduced by the forces of darkness. The story's equivalent of Riku.
- Adaptational Villainy: In his show of origin, he was the only thing standing between Zim and total annihilation of Earth. Now the tables have turned...
Zim's insane robot assistant and best friend who goes missing when their world is lost to the Heartless. The story's equivalent of Kairi.
Dib's Enfante Terrible little sister. She is lost along with GIR when the Heartless take their world.
A small, floating robot moose originally intended to replace GIR as Zim's assistant, but Zim ended up keeping both around. He is brought along with Zim to Traverse Town, but he chooses to stay behind when Zim leaves on his journey.
The king of the Comic Kingdom, Garfield is one of the first to notice how much danger the worlds are in, and one of the first to take action. When he leaves on a journey, he instructs Calvin and Hobbes to follow the Keyblade bearer. The story's equivalent of Mickey.
- Cloudcuckoolander: He is interestingly this to a very small extent: he appointed a teddy bear as the Secretary of State and no one knows why he named his kingdom the Comic Kingdom.
- Jerk with a Heart of Gold: He is implied to still be the jerk he is in the comic strip, but he still cares about the well-being of the multiverse.
The Grand High Deputy, who randomly shows up at various points of the story. The story's equivalent of Pluto.
The queen of the Comic Kingdom and the story's equivalent of Minnie.
The duchess of the Comic Kingdom and the story's equivalent of Daisy.
Garfield's head chef.
The Secretary of State.
A punk vampire and the leader of the Heartless Resistance in Traverse Town. When his actions attract the attention of Garfield, Garfield instructs Calvin and Hobbes to find him and obtain his help in locating the Keyblade bearer. The story's equivalent of Leon.
- The Nicknamer: "Limey" and "Small, Green, and Twitchy" for Zim; "Kit" for Naruto; "Sand Reaper" for Gaara; "Red" for Frankie; "Monkeyboy" for Ron.
A teenaged ninja working with Spike in the Heartless Resistance. The story's equivalent of Yuffie.
A ninja in the Heartless Resistance with the power to control sand. The story's equivalent of Aerith.
Traverse Town's resident mechanic who fixes up the Gummi Ship after Calvin and Hobbes crash it into the Monty Burns Casino. The story's equivalent of Cid.
A human-ghost hybrid from Nicktown who ended up in Traverse Town with Zim and several other Nicktown residents.
The ten-year-old creator of Bloo who is often a voice of reason.
Mac's egotistical imaginary friend.
An imaginary friend resembling a huge, hairy monster.
A man with the ability to quickly learn any skill and profession and execute them perfectly.
A talking one-year-old prodigy with a complete disdain for everyone else.
A megalomaniac robot in charge of overseeing construction work of new buildings.
- Berserk Button: Calling Ron "Monkeyboy".
The manifestation of what Zim could have been if he hadn't been evil most of his life.
- Bilingual Bonus: His name is latin for "charity".
The manifestation of Zim's guilt of his previous life as a villain. The story's equivalent of Tidus, he asks Zim what he's afraid of.
- Composite Character: Of Tidus and the Darkside boss.
A psychic little boy who plays the role of a psychologist and interrogates Zim about his past. He is the story's equivalent of Selphie and asks Zim what is most important to him.
A homicidal man who, as the story's equivalent of Wakka, asks Zim what he wants out of life.
Dib's Mad Scientist father who gave Dib his own laboratory complex after getting sick of his experiments disrupting everyone's lives.
Another child scientist who is one of the main contributors to Dib's Portal Generator project. Zim is mad at him for various reasons.
One of Jimmy's friends who constantly needs to be reminded that Zim is an alien. He might just be messing with Zim, though.
Another of Jimmy's friends.
Timmy's idiotic fairy godfather. His existence still isn't known to anyone else.
- Who Even Needs a Brain?: A Type IV example, he shows an x-ray revealing that his skull only contains some cobwebs and a sign saying "This Space for Rent".
Timmy's fairy godmother and Cosmo's long-suffering wife. Her existence still isn't known to anyone else.
A boy who makes movies using movie scripts that mysteriously appear at random spots in the town.
An evil plankton who was paid by an unknown entity to assassinate Zim. He does this by rigging the Portal Generator's basement to collapse in on itself once Zim completes the final steps of construction. The attempt fails, but he gets the money anyway.
A chihuahua whose only role is to be assaulted by other characters for being obnoxious.