He was the older brother of Liz Allan who was addicted to gambling to pay off his debts to Blackie Gaxton. He eventually became an unwitting test subject to the Green Goblin and turned into a supervillain under the Green Goblin's control.
He was voiced by Eric Lopez who also voiced the Witch-King of Angmar in the video game, The Lord of the Rings: War in the North and Bane in the video game, Young Justice: Legacy.
Mark Allan is the older brother of Liz Allan but became addicted to gambling. After suffering many losses in gambling, he stole a car to pay off his debts which got him arrested and sent to Juvenile Hall.
The Spectacular Spider-Man
Six months later, Mark is let out and he returns to Midtown High where he becomes attracted to Mary Jane Watson and the two start dating and she tries to get him to not gamble again but he goes back to it anyway. During Valentines Day, Mark and Mary Jane attend a date with their friends until Peter leaves to become Spider-Man to fight Tombstone, Silvermane and Doctor Octopus. This disappoints everyone and Mark refuses to let Peter see Liz by telling him that Liz is "too good for him" and it is shown that he is aware of Peter's feelings for Gwen Stacy.
Later, Mark tries to assure Blackie Gaxton that he will pay him off on the next horse race. Unknown to him, Green Goblin (having become the new Big Man of Crime) persuades Blackie to let him use Mark as a test subject for an experiment. Blackie Gaxton takes Mark to an abandoned police station where Norman Osborn (who is secretly Chameleon in disguise) and Dr. Miles Warren are in a secret lab where they insert nanobots into him which becomes successful which enables him to turn his fire powers on and off at will and he is cleared of his debts. Unknown to him, the Green Goblin has a control which makes him turn Mark's powers on an off. During the horse race, the horse that Mark had bet on comes last which causes him to angry and the Green Goblin turns on his fire powers. Spider-Man fights Molten Man but the latter defeats him easily and escapes. Returning to Blackie Gaxton at the Big Sky bar, he finds the Green Goblin also in attendance who reveals that he was the one who activated his powers through the control. He then blackmails Molten Man into helping him defeat Spider-Man and he will relinquish control over him. Spider-Man arrives and Molten Man battles him while destroying the bar and Mary Jane and Liz arrive and get caught in the crossfire while recognizing him as Mark. However, Spider-Man manages to save Mary Jane, Liz and Blackie Gaxton. The girls try to persuade him to stop gambling but he refuses to listen until Spider-Man "defeats" him by spraying water on him but the Green Goblin secretly turns off Molten Man's powers while he escapes. Molten Man is then taken to prison much to Liz's distrught.
Later when the Green Goblin takes control of the Vault, he releases many of its prisoners including the Molten Man to destroy Spider-Man. However, Spider-Man along with Black Cat and Walter Hardy are able to defeat the prisoners who are taken back to their cells.
In the comics, Molten Man was a scientist called Mark Raxton and is Liz Allan's step brother. However, this version of Molten Man is biologically related to Liz and also takes the place of Bennet Brant in gambling and his problems with Blackie Gaxton. His supervillain origins also differ when in the comics, he created an experimental metal alloy which accidentally spilled on him while in this series, he becomes a test subject for the Green Goblin to pay off his debts.