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"Hatman" is a recurring crude caricature of a Viacom New Media higher-up that the developers hated. Originating as paint graffiti of the person on a wall whose identity was disguised by putting a top hat on it, it soon made hidden appearances in the rest of the developer's output as an obligatory Easter egg. The earliest known Hatman Easter egg made for a game was a short CG animation for the game
Beavis and Butt-head in Virtual Stupidity.