Doom (1993 video game)
The ability for others to create custom levels and otherwise modify the game using WAD files turned out to be a popular aspect of "Doom". Gaining the first large mod-making community, "Doom" affected the culture surrounding first-person shooters, and also the industry. Several future professional game designers started their careers making "Doom" WADs as a hobby, among them Tim Willits, who later became the lead designer at id Software.
Clone (computing)
Since the existence of video games, clones of successful concepts and brands were common.
For instance, the influential first person shooter Doom lead in 1990s to the creation of a new genre dubbed as Doom clones. In the 2000s the open world action-adventure Grand theft auto inspired the creation of many Grand Theft Auto clones.