Original Fallout coded in just over two weeks
One interesting snippet out of GDC 2012 explains how a licensing issue forced Interplay to recode the game in a fortnight.
As reported by Destructoid, Tim Cain, one of Fallout's key designers, gave a classic post-mortem on the much loved role playing game.
He revealed that Steve Jackson Games, the pen and paper RPG company, took exception to Fallout's gore and dark humour, and canceled Interplay's GURPS license.
The team feverishly invented a new role playing system from scratch, later known as SPECIAL; Cain said he was going to call it ACESLIP until someone else - probably a better Scrabble player - pointed out a nicer acronym. The game was coded on this new backbone in two weeks, although the now-famous Perks system was added later.
Fallout released in 1997 and is considered one of the highlights of the golden era of PC RPGs. It spawned a sequel and a tactics spin-off, and inspired the licensed, Bethesda-published games of the same name.