The design of the bad guy, Evil Otto, is based on the smiley face made popular in the 1960's. The developer, Alan McNeil, despised the image, because he felt it depicted a kind of "fake friendliness" he associated with businesses and salesmen. He made Evil Otto into a Smiley just to add a little sarcasm to the game, imagining the tagline "Have a Nice Day!", which frequently accompanied the smiley face, as here meaning "Have a Nice Day while I beat you to death."

Evil Otto's name, however, comes from the security manager at Alan McNeil's previous employer, Dave Nutting Associates: Dave Otto. Nobody at DNA liked Dave Otto, because he instituted strange and annoying policies, which Alan collectively described as "you are all guilty until proven innocent".