What if the protagonist of the horror/sci-fi FPS series Doom had been given an appearance roughly resembling that of the protagonist of the horror/sci-fi movie series Alien? Alien was a big influence on Doom after all, and id Software could've easily been influenced by it even more. Such a tiny change could've given birth to a whole army of space marine butterflies, in my opinion, Doom being the grandfather of today's most popular and profitable video game genre.