Mister Plastic (Reed O'Brian) - superhero with shapeshifting ability. Professor O'Brian was irradiated at Chernobyl exploration mission. He tried himself at robbing, but some time later he become hero and the leader of the Four.
Light Lady (Sue Hoshi) - half-Japanese half-American sciencist Susan was irradiated at Chernobyl and got light manipulation ability. Later married Reed.
Flaming Torch (Johnny Raymond) - young sciencist and football player. After irradiating in Chernobyl, he got flame manipulation superpowers.
Metathing (Ben Mason) - Reed's best friend and massive body superhero with stone skin and heart. His love interest is Alice Stagg, the daughter of the evil mastermind Philipp Stagg.
Doctor Mongul (Victor von Mongul) - The ruler of the warlike country "Warveria", Victor von Mongul is a great scientist and magician. A former friend of Reed's and the carrier of the Mask of War.
Doctor Mongul II (Kristoff von Mongul) - Kristoff is Victor's nephew and the next wearer of the mantle and mask of Doctor Mongul.
Lady War (Mongal Vukovic) - Mongal fanatically loyal to Dr. Mongul, at one point becomes his bodyguard and carrier of cosmic power.
Puppeter (Philipp Stagg) - Evil mastermind and stepfather of the Alice Stagg - Ben Mason's fianceé.
Diamak (Henry de Ablo) - Crazy sciencist and T-Rex's creator. He got his superpowers after drinking super-potion.
T-Rex - strange giant monster, created by Diamak. He can flamebreath and fly.
Multiwizard (Bentley Black) - strange super-villain who had team-up with Glue King.
Glue King (Buddy Petrusky) - strange super-villain who had team-up with Multiwizard.