In Metal Gear Solid 4, the all-female haven troops cannot be knocked unconscious by grabbing their crotch after a body search (as it turns into a grope). If Snake tries this, the soldier will start yelling "Pervert!", "You idiot!", "If you don't cut that out...", or "You men are all the same!" They will soon retaliate with an incapacitating kick. That said, there's a slight chance they will say, "Hey, you're pretty good at that."

Throughout Old Snake's character development, Hideo Kojima and his crew did extensive research to find out which mustache would work best for Old Snake. They settled for the mustache of Lee Van Cleef from the 1966 film "The Good, the Bad, and the Ugly". Additionally, ever since Metal Gear Solid 2: Sons of Liberty, the team played around with the idea of Snake's facial hair growing in real time.