- Dragonfly-Robin Atkin Downes
- Bonzai Bill/Chaser-John Moschitta Jr.
- Sparky/Skullex-Richard Steven Horvitz
- Pangolin-David Gallagher
- Tech/Vlad the Impaler, Human form-Yuri Lowenthal
- Vlad the Impaler, Vampire bat form-Steven Bateman
- Demona-Grey DeLisle
- Gauntlet-Sam Riegal
- C.A.B.-Frank Welker
- Caerrian Sentinel-Tara Strong
- Aku-Jason Marsden
- Ace-Tom Everett Scott
- Muscle-Janice Kawaye
- Arachnion/Spider-Man-Josh Keaton
- Sky Pterror-Doug Parker
- The terrible Terrapin/Cyber-Soldier-John Di Maggio
- Archelon-Sean Schemmel
- Ghoul/Magneto-Christopher Judge
- Dr. Nicodemus-Kent Williams
- Winston Riker-Dan Green
- Mantis-Don Brown
- Moonshine/Meta Man/Street Reaper-Dee Bradley Baker
- The Ocelot-Stephanie Sheh
- Bone Master/Triple-Threat/Rat Man/Pavlov/Draco-Scott McNeil
Season 1 deals with the Offbeats origin with a three part episode then moves on to them struggling to prove themselves as a superhero group. Because of the fact that the Offbeats are relativley unknown at this point the main villians for this season are Sky Pterror and the Dino-Gang and a series of smalltime thugs who don't appear in the comics. The season finale pits them against the Trinity of Terror.
Having succesfully gained recognition and slight fame the Offbeats have moved on to become a stronger team and have gained a reputation. Because of this however they have gained a larger rogues gallery. The primary antagonists of this season are the Terrible Terrapin, Archelon and Skullex. The season finale has Magneto's acolytes team up with the Terrible Terrapin in an attempt to finally put a stop to the Offbeats once and for all.
Having beaten Magnetos acolytes the Offbeats have become a household name and the other superheroes are finally starting to show respect for the Offbeats and stop being so suspicous of them, even occasionally helping them. Dr. Nicodemus shows up in this season, along with Mantis, Viper, Winston Riker and the Gorilla Gang. In the Season finale the Caerrians show up and attempt to destroy New York only to fail when confronted by the Offbeats.
Reeling over the death of the C.A.B. the team attempts to recruit more members and meet the Rabble-Rousers who eagerly join the team. The Caerrians are the main villians of the season, along with Skullex. The season finale involves the return of the Trinity of Terror and Magnetos acolytes.
Differences from the comic
In the TV series Bonzai Bill is shown to talk much more rapidly than he does in the comics and is something of a yes-man, always sucking up to Dragonfly. Rather than the Rabble-ROusers force their way onto the team as they do in the comics the Offbeats actually recruit them. The Trinity of Terror are also signicantly toned down as well due to their particualarly psychotic nature in the comics.
- During the Caerrian invasion Sparky says "Let me deal with this, I've had experience with aliens before." This is an obvious reference to the fact that Richard Steven Horvits did the voices for two alien characters.
- Another Invader Zim reference is when a virus infects C.A.B. and causes his voice to become higher, his eyes become cyan and he starts acting randomly and crazily while yelling out "Taquitos!" among other non-sequitors.
- Christopher Judge who voices Magneto also voiced him in X-Men evolution.
- Josh Keaton also voices Spider-Man in the newest Spider-Man TV series.