Season 1 (Transformers Unite):
Autobots:
Optimus Prime - Legendary Autobot Leader (Semi Truck)
Hot Rod - Rebellious Autobot Youth (Sports Car)
Catapult - No-Nonsense Autobot Scout (Baja Buggy)
Showdown - Big-Hearted Autobot Brawler (Monster Truck)
Doubletake - Strict Autobot Officer (Police Car)
Triage - Short-Tempered Autobot Medic (Ambulance)

Decepticons:
Megatron - Legendary Decepticon Tyrant (Futuristic Tank)
Shockwave - Logical Decepticon Scientist (Spaceship)
Firebreaker - Decepticon Hacker (Fighter Jet)
Astraea - Decepticon Security (Pickup Truck)
Drive-By - Decepticon Ripper (Hearse)
Rampart - Decepticon Gladiator (Tank)


Season 2 (Treasure Hunt):
Autobots:
Cameo - Cheerful Autobot Ninja (Motorcycle)
Outsider - Autobot Loner (Surfer Bus)

Decepticons:
Deadhead - Braggart Decepticon Speedster (Sports Car)
Diabla - Decepticon Huntress

Seacons:
Sky-Byte - Seacon Captain (Robotic Shark)
Snaptrap - Seacon First Mate (Robotic Turtle)
Seawing - Seacon Spy (Robotic Manta Ray)
Skalor - Seacon Bruiser (Robotic Coelacanth)
Tentakil - Seacon Deceiver (Robotic Squid)
Nautilator - Seacon Tracker (Robotic Lobster)

Others:
Anomaly - Toxic Cybertronian Mutation (Tanker Truck)


Season 3 (Quintesson Quest)
Insecticons:
Insecticon Shockwave - Insecticon Leader (Spider/Spaceship)
Venin - Insecticon Second-In-Command (Wasp/Jet)
Ransack - Insecticon Thief (Locust/Motorcycle)
Hardshell - Insecticon Bruiser (Rhino Beetle/Jet Car)
Zaptrap - Insecticon Barrage (Stag Beetle/Armored Car)
Starcloud - Insecticon Medic (Ladybug/UFO)

Aliens:
General S'gnarr - High-Ranking Skuxxoid Warlord
High Judge Chitix - Antillan High Judge
Head Master Zarak - Nebulon Leader

Others:
Starscream - Former Decepticon Turn-Coat (Futuristic Jet)


Season 4 (Return to Cybertron):