Going by the timeline theory, Arnie was born around the year 1159. (Parents) At age six he and George were infected with Rigaelean flu and are bethrothed by proxy. Arnie was bethrothed to Xil. (Girlfriend)
Arnie was once the superhero named Polarman, he lost his powers because he began charging for his services. He later lived his on Earth, owning a Snack Bar in Brooklyn, which was notorious for it's bad food. Arnie often scammed a gulible customer via bets on football matches he recorded with his VCR.
George comes to Arnie's Bar as he needs his advice, as he met Janet, a great girl but there's a problem. Arnie initally thinks she's from Zargus but George says he doesn't think she wants to go out with him. Arnie is shocked that she doesn't want to go out with Thermoman, but George reveals that he met her as his normal self. Arnie suggests George gives Janet a present and if she likes it, he asks her out. It turns out well, and he goes out to dinner with her. George has to decide what to do next, and goes to Arnie for help. When he reveals his present for her was surgical stockings, Arnie affirms he does need help. Arnie suggests he takes her back to his place and shows her "the money", saying that if she likes him as George "surgical stockings" Sunday she'll love him as Thermoman, saying he's Tom Cruise in tights, "only taller". (My Hero)
Arnie next appears trying to sell a watch to a customer, apparently it was owned by a "sweet old guy" who came to his bar every day for coffee and danish, after he croaked. The customer points that Rolex only has one 'l', though Arnie says he's complaining about spelling on a watch that good, Arnie manages to sell it. George comes to the bar, Arnie compliments what he did with the Earthquake in Nevada. George gives Arnie something of his he found in the Earth's core, Arnie says that he'd get it himself.
- When Arnie moves to England, as far as the taxman knows, his name is "Felicity Smith". (Taking the Credit)
He, throughout the series has been helpful and resourceful to Thermoman, on matters such as contacts on Ultron and advice to help George when in need.
He's a greedy character, willing to do anything to make money, regardless of who it harms, including himself. In one episode he gets his powers back from the Ultron Council, and becomes the new hero in town, as it were, making George feel redundant. He has them taken away again when caught stealing from those he saved, and even for stealing the Crown Jewels. In series one, he lives in New York, where he owns a café, but moves to Las Vegas in series two, where he owns a casino and to Northolt in series three. From series three onwards, Arnie starts using British idioms, whereas in series one and two he uses American idioms.
Examples of his attempts to become rich are trying to start up a website for George's health shop with Tyler that does well for a day, then Tyler accidentally destroys the website and his laptop. He makes 80 pounds per week in six months while filming a sitcom called "the filth channel" for Ultron recording his activities with Mrs Raven. He starts a therapy to help George get his invincibility back when he learns the truth about his powers and he makes 60 pounds, but Janet gets him to reduce the price.