Tim Cain has explained that Steve Jackson Games disliked several aspects of the early Fallout project, including its cheerful Vault Boy mascot. The disagreement centred on the contrast between Fallout’s extreme violence and Vault Boy’s upbeat presentation, which the company felt trivialised the game’s serious post-apocalyptic themes.

Fallout was originally intended to use Steve Jackson’s GURPS role-playing system, but the licensing arrangement collapsed after objections to the game’s tone and content. Cain says Steve Jackson Games also disliked the violent opening sequence and the game’s small-scale character designs; the developers ultimately created their own SPECIAL system, while retaining Vault Boy, which became one of Fallout’s defining icons.