Wolverine's appearance in this show has him speak in an Australian accent, voiced by Neil Ross, despite the character being from Canada in the comics. Wolverine also has an Australian accent and again voiced by Ross in Pryde of the X-Men (1989). In the live action X-Men film series that began in 2000, ironically, the character is portrayed by the Australian Hugh Jackman.
The character Videoman was created exclusively for this series. Initially, Videoman was a villain, but with the video game craze of the 1980's, Marvel thought the character had more potential as a hero instead of a villain and set him up to be included in the X-Men for their own series pilot.
Doctor Octopus was the only super-villain to cross over on three shows (this one, The Incredible Hulk (1982) and Spider-Man (1981). Michael Bell voiced Doc Ock both this series and the Hulk cartoon which aired on NBC on Saturday mornings at the same time.
Originally, the Human Torch was going to be in the series with Spider-Man and Iceman. Licensing issues at the time prevented the use of the Human Torch and so Firestar was created to fill the open spot. Firestar has similar powers as Human Torch, but doesn't have the appearance of being on fire.
During initial discussions, the creative team went to NYC for a meeting with NBC VP of Children's Broadcasting, Mickey Dwyer, and one of the things she wanted for the show Firestar to have a dog. Writer Dennis Marks' wife had had a Llhasa Apso, a rather new breed in the States at the time and he told Ms. Dwyer about the Llhasa being the Temple Lion Dog of Tibet, and, because this was right in the middle of the feminist revolution they decided to could call the dog character "Miz Lion." That character sold the show to NBC.
Only three villains made return appearances after their first appearance on the show: Magneto (in a brief flashback in "A Firestar is Born"), Electro (in a cameo appearance in "Attack of the Arachnoid"), and Videoman (who appeared in "Videoman", "The Origin of Iceman, and "The Education of a Superhero").
Dan Gilvezan initially read for the part of Spider-Man and got the role.After waiting to hear back from NBC, he was told by voice actress Sally Julian that they did the first session last week and that he had been recast. Two weeks later, Gilvezan's agent called and said he was booked to voice Spider-Man because NBC wasn't satisfied with the person they chose after all. All of Spider-Man/Peter Parker's lines in the first episode had to be redone with Gilvezan's voice added in.