Alien Hominid is a side-scrolling shooter in a similar vein to games such as Metal Slug, where one hit instantly kills and has a two-player simultaneous play. Players take over as the titular hominid, who has to fend off waves of secret agents. His main arsenal is a blaster, while players can also melee close-up enemies and use a limited number of grenades to attack. Advanced moves include rolling under shots, jumping on and biting off enemies' heads, temporarily scaring other enemies, and digging underground to drag enemies down with them.
Alien Hominid began as a Flash game developed by programmer Tom Fulp and animator Dan Paladin, which was released on Newgrounds in August 2002. It's often referred to as the Alien Hominid "prototype" by The Behemoth. The game consisted of one level containing two bosses, who would later reappear in the retail version. It became very popular among the online gaming set and has been played over 20 million times. Later in the year, then-co-worker John Baez approached Paladin as a fan of Alien Hominid. He suggested that Paladin and Fulp make a console version of the game, even offering to produce the game. Both Paladin and Fulp agreed with his idea, forming The Behemoth.
In the course of two years, Alien Hominid became a much larger project than its online prototype. While 3D graphics were considered initially, The Behemoth decided nothing compared to the traditional 2D stylings of the prototype. The project was entirely re-coded for consoles, and many new gameplay features were created. Matt Harwood created the music for the game.