Happyman is likely one of, if not the first entity that you may encounter in the game, as this entity can spawn at any room past the lobby.

Happyman appears to be a basic, presumably hand-drawn, red smiley face that can open its mouth to talk occasionally. When it’s mouth is open it presumably has zero teeth inside its mouth, and the inside of its mouth is seemingly nonexistent, this applies to most other Happyman variants (exceptions are Bigman and Glee and the variants that have visible teeth