Gaster is an enigmatic figure connected to hidden lore in Undertale, Toby Fox’s 2015 role-playing game. Fans frequently associate the character with secret rooms, unusual encounters, and deliberately fragmented clues. The specific figure often shown vanishing is widely called Mystery Man, although the game does not directly confirm that identification. The brief effect spread through Undertale fan animations, lore videos, memes, and soundboards, where it became shorthand for an uncanny disappearance. It remains useful because the reference is recognizable while the timing fits quick modern edits.