In the book Masters of Doom, author David Kushner asserts that the concept was discussed only briefly during a 1991 telephone conversation between Underworld developer Paul Neurath and John Romero.
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The credits for the series are Mike Maynard, James Row, Nolan Martin (programming), Steven Maines (art direction), Carol Ludden, Jerry Jones, Adrian Carmack (art production), James Weiler, Judi Mangham (quality assurance), and id Software (3D imaging effects).