Zick is the main hero of the series. A young loner with allergies, Zick is called weird by everyone else. He is a Monster Tamer.
- Betty and Veronica: The Betty to Teddy's Veronica for Lay's Archie, and the Archie for Elena's Betty and Lay's Veronica.
- By the Eyes of the Blind: He's able to see monsters and apparitions that others cannot. It runs in the family.
- Blessed with Suck: Sometimes sees his powers as this due to dealing with Bombo's shenanigans and his responsibilities as a Tamer. As such, he longs for a normal life.
- Last-Name Basis: 'Zick' to everyone. Even his parents call him Zick. His dad on the other hand, is called Zob by everyone.
- Loners Are Freaks: Gets this treatment in school.
- Spider-Sense: Has allergies that alert him whenever an evil monster's on the prowl.
- Tomato in the Mirror: Zick is a monster, as with all tamers.
- You Gotta Have Blue Hair: Shares this with his dad.
Elena is the main heroine of the series. She is Zick's best friend. She later becomes a Monster Keeper.
- Action Survivor: Even before she had the Sight Dom, she's helped Zick out of more scrapes than he'd like to admit.
- Badass Normal: Even though she only has the Sight Dom, she's tough.
- Betty and Veronica: The Betty to Lay's Veronica for Zick's Archie.
- By the Eyes of the Blind: Starts out unable to see monsters, but near the end of the first season, she's given the power of the Sight Dom by Greta.
- Catchphrase: "Holy spit!", changed to "Holy sneeze!" in the American Kids' WB! broadcasts.
- Clingy Jealous Girl: When Zick's around Lay.
- Hair Decorations: Tends to have a pair of bows attached to each of her pigtails.
- I Just Want to Be Special: For a good part of the first season, Elena longs to see monsters, and eventually gets her wish.
Magnacat is the main villain in season 1. He is the president of Pyramid Inc., but in reality, he is a shape-shifting Gorka. His main plans are attempting to take over Bibbur-Si.
- Big Bad: Of season 1.
- Surrounded by Idiots: When it comes to Omniquod and Omnised.
Moog Magister is the main villain in season 2. He is the lord of the Anguanes.
Hector Sinestro is the main villain in season 2. He is a Dark Tamer who tries to get revenge on Zick's father, Zob.
- Revenge by Proxy: Why he targeted Zick instead of his father.
Omnised and Omniquad
The two Gorka brothers and Magnacat's minions.
- Sinister Shades: When in their human forms
Omnised and Omniquad's replacement after the two are captured.
- Canon Foreigner: Exclusive to the cartoon.
Zick's aunt and an Anguane.
- Sitcom Arch-Nemesis: She dislikes Greta for marrying her nephew.
- By the Eyes of the Blind: Is also able to see monsters and ghosts. Though she feigned ignorance of this early in the first season, for Zick's sake.
- Inherent Gift: How Greta could pass the gift of sight to one person.
- Meganekko: Is always seen wearing glasses.
Zobedja "Zob" Zick
- Action Dad: Even when shrunk, he can still kick some butt.
- By the Eyes of the Blind: Able to see monsters and ghosts, as well.
- Disappeared Dad: Earlier in season 1, but came back as the Incredible Shrinking Man.
- You Gotta Have Blue Hair: Shares this with his son.
Theo Barrymore and Tessa Grange
Zick's maternal grandparents and white ghosts.
Ezeria Zick and Maria Bertold
Zick's paternal grandparents.
Harvey is Elena's father.
Elena's mother. Later in the series, she gave birth to twins, a boy and a girl (in the comic book series, their names are Charlie and Violet).
Elena's 8-year-old cousin.
Elena's pet cat.
- Hidden Depths: As stupid as he is, Purrcy has some awesome skills, such as making sand castles with his litter.
Elena's pet rabbit. In the comic book had a run-in with a Digesting Plant, with long-term effects.
- Boxing Lessons for Superman: Deputy-Deth had it trained to hunt Tamers. Part of the training included learning kung-fu.
- Killer Rabbit: Becomes a dangerous part-monster after the run-in with the Digesting Plant, especially after Deputy-Deth had it trained to hunt down Tamers.
- Stuff Blowing Up: After his training with Deputy-Deth, he can cut carrots in perfect halves with flying kicks, the carrot then exploding.
One of the monsters in Zick's house under the supervision of Timothy, and later by Jeremy. He likes eating Zick's shoes, and cries when taking a diet. His crime is ignoring his diet and stealing some cakes.
- Beware the Nice Ones: If motivated enough, Bombo can easily deal with any opponent by eating it. Just ask Zick's out-of-control Dom.
- Big Eater: Even for a Bombo, hence his criminal record.
- Denied Food as Punishment: Forced to go on diets that lasts only a couple of seconds whenever he misbehaves.
- Heroic Sacrifice: In the comic: when Zick's out-of-control Dom tries to devour Zick, Bombo reacts by eating it, resulting in him becoming Zick's Domulacrum to reabsorb his Dom.
- Third-Person Person: Does this all the time.
- Trademark Favorite Food: Shoes. He tends to like Zick's the best, but he'll eat anyone's, given the opportunity.
- You No Take Candle: Bombo isn't really the most...eloquent monster, to say the least.Bombo: No worry, Zick, Bombo has it all figured out. Bombo left Timothy a decoy—a dummy that look just like Bombo.
Snyakutz Bu is another monster in Zick's house under the supervision of Timothy and later by Jeremy. His crime is littering (leaving pieces of himself everywhere).
- Extra Eyes: Has two extra ones on top of his head, with one in particular on a stalk.
- Eye Pop: Quite literally, in this case. Whenever Bu gets frightened or knocked over, there's a good chance his eyes will pop out, along with other parts of his body.
- Eye Spy: In "A Monster for Two", Bu uses one of his eyes in combination with Zick's Sight Dom to see where Scabby and Grood are hiding out.
- What the Hell Is That Accent?: In English adaptations of the comics, he tends to have a vaguely French accent whenever he speaks. Averted in the English dub of the series, where this is dropped.
- Blob Monster: Fits the bill quite nicely, as does his entire species. Blobby? Check! Jelly-like? Check! Able to stick and hang from surfaces? Check and checkmate!
- Dreadful Musician: Loves to play the violin, but is terrible at it.
- Those Two Guys: Him and Ben-Talak. They're together all the time and one is never seen without the other close by.
- Blob Monster: Shares this with his species and his co-hort, Clak-Ritak.
- Those Two Guys: Him and Clak-Ritak.
- Attention Whore: To the point he will risk the entire monster world by making himself visible.
- Dude Looks Like a Lady: With his pink skin, bright red lips and stylized hair, it's fairly easy to mistake Chumba as a woman at first glance.
- Too Dumb to Live: Many of his attempted escapes should have resulted in his death. Even the very fact he tries to escape counts, as any Detention Oasis is put in a place that is extremely dangerous to most monsters and trying to go outside could easily result in death-and he knows perfectly well since the one escape attempt that actually succeeded resulted in the two Dark Phantoms mentioned above almost eating him.
Zick's cat and Tutor. A very mysterious and sarcastic being, but a great help to Zick. He is the leader of the Barrymore's Detention Oasis.
- Extreme Doormat: In "Zick vs. Zick", he takes responsibility for giving Zick freedom and is forced to obey Jeremy-Joth by leaving the house. However, they seem to come to good terms in "The Horn of Kong".
- Jerk with a Heart of Gold: He can be quite hard on Zick and the monsters in his Detention Oasis, but usually not without reason, and deep down, he does care about them.
- Mentor Mascot: A Tutor who takes the appearance of a cat and teaches Zick what he needs to know about the monster world and being a Tamer.
- Noodle Incident: He's a Star Tutor, the star being a decoration for incredible valor that is given once every hundred years. What he did to earn it has never been explained.
- Put on a Bus: He leaves the Barrymore house in "Zick vs. Zick", but returns eight episodes later in "The General Inspector".
One of the four Maximum Tutors. Strict and mean, Jeremy replaces Timothy as the leader of the Barrymore's Detention Oasis after the latter broke many of the rules of Bibbur-Si. Later, he steps down from that position, allowing Timothy to return, and, in season two of the animated series, becomes the leader of the Ancient Armory.
- Alliterative Name: Jeremy-Joth.
- Big Damn Heroes: In his first appearance, Jeremy shows up to scare Omnised and Omniquad away.
- Cats Are Mean: Subverted in that he's not really a cat, but a Maximum Tutor.
- Drill Sergeant Nasty: He has no problem yelling and bossing around both Tamers and Monsters alike as long as it gets results.
- Establishing Character Moment: In his first appearance, he sends Omnised and Omniquad off running and is shown to have a strict and nasty attitude.
- Good Is Not Nice: Has this in spades right from the get-go. He does lighten up over time, though.
- Jerkass: In "Zick vs. Zick", he tells Elena to leave and later kicks Timothy out of the Barrymore house for breaking a lot of rules and refuses to allow Zick to say goodbye to him. He also treats Zick and the other monsters like crap and zaps the former's shoes without regret.
- Jerk with a Heart of Gold: He does have a caring side for Zick and Elena, as shown in "The Devourer".
- No Indoor Voice: Shouts a lot. It's practically his normal tone of voice.
The only female cat and Tutor (in the cartoon). She is in charge of the Detention Oasis at Port Reef.
- Only Known by Their Nickname: Her real name is actually Larraby-Tuth, but prefers to be called by her nickname Lardine.
- Seen It All: Her monsters are completely insane (enough to drive Timothy crazy when they're temporarily entrusted to him), and dealing with them has left her unable to be surprised by anything.
- The Smurfette Principle: At least in the animated series; the comic features a number of other female Tutors.
- Surrounded by Idiots: Her monsters aren't very bright. Once, they tried to escape by hiding in a picnic basket.
Tadduja "Teddy" Thaur
A 14 year-old Tamer, and one of Zick's friends. He is a show-off, arrogant and boastful to anyone. He sometimes respects Zick, but not Elena that he always call her Potato.
- Betty and Veronica: The Veronica to Zick's Betty for Lay's Archie.
- Butt-Monkey: Is this for season 2.
- Jerk with a Heart of Gold: Can be at times, but is not one for leaving his fellow Tamers to die.
Terrentuja "Terrence" Thaur
A 14 year-old female Tamer, one of Zick's new friends. She is admired by the young male Tamers, including Teddy and Zick, a reason that Elena is a bit jealous of her.
- Action Girl: Par for the course as a Tamer.
- Bare Your Midriff: Tends to wear clothing that show off her belly quite a bit.
- Betty and Veronica: The Veronica to Elena's Betty for Zick's Archie, and the Archie for Zick's Betty and Teddy's Veronica.
- Dude Magnet: Both Zick and Teddy have the hots for her, much to Elena's dismay on the former.
- Hot for Teacher: In the comic series, she has a crush on her teacher Dan Tulasech.
A new young Tamer in the Ancient Armory, and a new character in the second season of the animated series. He is very handsome and popular among the girls in the Armory especially Elena and Lay, which made Zick a bit jealous of him.
Patty Smirnov and Mattie O'Hare
Patty and Mattie are the two school journalists who tease Elena for hanging out with Zick.
- Laser-Guided Amnesia: When they found out about the world of monsters.
- Paparazzi: As journalists, they love digging up any good dirt and passing it along.
David is a bully who picks on Zick, but stops bullying him once he becomes Annie's friend.
An ex-Tutor Maxim out of the job because of abusing power.
- Baleful Polymorph: His ultimate fate: he's turned in an actual cat for good.
- Jerkass Has a Point: Has an annoying habit of making some fine points, especially when he's being a jerk. One moment above all is when he's at Zick's home to prevent him and Greta from assisting Timothy, Jeremy and the adult Tamers (currently fugitives from the law): he forces Zick to carry around a retrained were-Puffy and never leaves Greta, and Zick still escapes surveillance and Greta bolts the very moment he lets her shower alone on condition she sings to prove she's still there (Greta has Bombo sing in her place).
- Karmic Transformation: He's turned into a regular cat on being defeated, the very punishment he wanted to inflict on Timothy and Jeremy.