The game was originally pitched by Telltale as a spin-off of Valve's Left 4 Dead franchise, but Valve turned down the pitch leaving Telltale to go to Robert Kirkman to successfully pitch him a game based on his Walking Dead comic book series. The same unique choice-based story-driven style of gameplay was kept by Telltale developers between the canceled Left 4 Dead project and the greenlit Walking Dead project, which the devs thought was a better fit for Kirkman's universe than Valve's franchise anyway and which would also be a style that would be reused heavily by Telltale in their later licensed games.
Contributed by PirateGoofy