In Undertale, we all know there are two known and shown humans in the game (those obvious being Frisk and Chara) but there is a secret third one that shows up when doing some kind of thing in waterfall where the player is with monster kid, that being a third one that gets triggered with doing some keyboard thing in the game where the reflection of frisk changes to this unknown human

Nobody knows what this is supposed to be as it's a unsolved mystery. Some people say it's an unused character or some believe it's a different version of Chara, whether the theory or what people think, we may never know what this unknown human is really supposed to be

Undertale by Toby Fox and Temmie chang

Art by Me