After defeating Psycho Mantis and listening to his final words in the Japanese version of the game, Mantis will say "it feels nostalgic." In the English version, the dialogue is changed to "it feels kind of nice," although this was then changed back into "it feels nostalgic" in the remake Metal Gear Solid: The Twin Snakes.

According to Hideo Kojima, the "nostalgia" that Mantis refers to is from him sensing his own mother's feelings during childbirth, where she used the last of her strength to help him survive.