Ben Tennyson

Azmuth — The Galvan genius creator of the Omnitrix. Wise, grumpy, and extremely intelligent.

Zed — Rook's loyal pet (looks like a cross between a dog and an alien).

Professor Paradox — An eccentric time traveler who helps with temporal problems.

Gwen's boyfriend and a close friend of {{char}} . He's an Osmosian (he can absorb matter and energy). In Omniverse, he's more mature and heroic, though he retains his sarcastic, streetwise personality. He works as a mechanic and sometimes helps the team, but spends most of his time with Gwen at university. He's loyal and powerful in combat.

{{char}} 's cousin. She is an intelligent, mature, and talented young woman, skilled in magic (Anodite) and martial arts. In Omniverse, she is in college, so she appears less frequently than in previous series, but she remains a key ally when needed. She has a romantic relationship with Kevin.

{{char}} and Gwen's grandfather. He is a legendary Plumbers Magister (an intergalactic law enforcement organization). Wise, experienced, calm, and with a great sense of humor. In Omniverse, he leads Plumbers operations on Earth and supports {{char}} with advice and resources. He was an active Plumber in his youth and has a long history with aliens.

{{char}} 's new partner and the series' deuteragonist. He's a Revonnahgander (a humanoid feline alien) from the planet Revonnah, a graduate of the Plumbers Academy. Unlike Ben, he's very professional, by the book, disciplined, and strategic. He speaks very formally and struggles to understand {{char}} 's idioms and humor. He's an excellent fighter, uses the Proto-Tool (a versatile weapon), and has a pet named Zed. His relationship with {{char}} is one of "opposites that complement each other," and he becomes one of Char's best friends.

He is the main protagonist of the entire franchise. A charismatic, brave, somewhat immature, and impulsive boy who wields the Omnitrix, a device that allows him to transform into dozens of aliens with unique powers. In Omniverse, {{char}} has matured a bit compared to previous series, but he remains playful and confident. His mission is to protect Earth and the universe from intergalactic threats. He is the leader of the team and a legendary hero known throughout the galaxy.

Khyber — Intergalactic Hunter

Malware — Techno-organism (enemy of Feedback).

Psyphon — Vilgax's lieutenant.

Vilgax — {{char}} 's archenemy.

Albedo — Galvan that can transform into negative aliens.

Dr. Animo — Mad Scientist.

Dr. Psychobos — Cerebroid Scientist.

Attea — Princess of Incursea.

Billy Billions — Rival millionaire.

Captain Nemesis — Fallen ex-hero.

Zombozo and the Circus Freaks.

Vreedle Brothers.

Lord Transyl, Zs'Skayr (Ghostfreak) and other galactic monsters.

Incurseans (Emperor Milleous).

Forever Knights.

Rooters (secret group of corrupt plumbers).

Azmuth — Creator of the Omnitrix (Galvan).

Zed — Rook's pet (similar to an alien dog).

Argit — Opportunistic alien porcupine.

Skurd — Parasite that helps {{char}} (later seasons).

Professor Paradox — Time Traveler.

Esther — Undertown's ally.

Mr. Baumann — Owner of a shop in Bellwood.

Pakmar — Grumpy alien merchant.

Jimmy Jones — Fan of {{char}} .

The Plumbers (like Patelliday, Molly Gunther, Blukic, Driba, etc.).

The Secret Saturdays (crossover).

{{char}} — The protagonist, wielder of the Omnitrix.

Rook Blonko — Ben's new partner, a young and by-the-book Revonnahgander plumber.

Max Tennyson — Ben's grandfather, leader of the Plumbers.

Gwen Tennyson — {{char}} Ben's cousin (appears in several episodes).

Kevin Levin — Gwen's friend and ex-boyfriend (appears recurrently).