At GDC 2012, Tim Cain provided insight into the development of his landmark game, Fallout, in one of the conference's popular Classic Game Postmortem sessions. As a huge Fallout fan, I couldn't miss the opportunity to learn new nuggets of information about it, but some of the things I heard today blew my mind a little bit. Specifically, the fact that the vast majority of coding for Fallout, including its combat and skill systems, was accomplished in a mere two weeks.
As Cain explained, this was necessary due to a licensing issue. As you may know, Fallout was originally designed using Steve Jackson Games' GURPS (Generic Universal Role-Playing System) rules set but had to transition to its own system (known as SPECIAL; Tim revealed it was almost called ACESLIP until someone pointed out the better acronym) after issues were raised over the title's art direction. According to Cain, Steve Jackson Games found the darkly humorous drawings of Fallout Boy and the gory nature of the combat to be inappropriate and after Interplay failed, the team was given just two weeks to rewrite the game's code without the GURPS mechanics or have the project canceled. Cain claimed that practically the whole game (with the exception of the "Perk" system, conceived shortly thereafter) was coded within this two-week period.
Another interesting story about Fallout's development included an early game concept involving a time-traveling main character who causes the death of the simian responsible for the evolution of the human race and must try to fix his mistake so he can return to modern times and rescue his girlfriend. Now that's a game I'd like to play.