According to a 1998 The PlayStation magazine interview with director/producer/writer Hideo Kojima & designer/artist Yoji Shinkawa, they commented about designing the character Psycho Mantis, specifically how elements such as him wearing a gas mask because he had "no face" were "part of expanding and developing the story", according to Shinkawa. Kojima clarified that while he didn't know why Shinkawa made those choices, he was not against them being made, stating that "unexpected things like this are part of the fun".

Early concept art of Psycho Mantis by Shinkawa includes notes that read: "His body is like a preying mantis, spindly and emaciated. He wears a mask to hide his ugly face." and "Is this Psycho's secret real face?"