Prismo's Time Room is the room where Prismo grants wishes. While in the room, all changes that the wish has made to reality aren't experianced, but can be watched on a screen on the side of the room.
Description[]
The Time Room has yellow walls with a giant moderating screen, which Prismo can use to watch over a person's wish, such as Finn while he was Finn Mertens after he wished The Lich never ever existed.