Uboa (EntityTopic, 7)
From Compile Worlds
Uboa is an alternative dweller of Poniko's house in Yume Nikki. He might even just be an alternative Poniko.
He appears randomly if you turn off the light in her room. Once you see him, there is no turning back. You are trapped. You can only make one more move, which is to touch Uboa himself and get teleported to what can only be described as Uboaspace, a looping, empty world with swampy ground and a haunting background.
Despite this, many still play Yume Nikki for the sole purpose of finding Uboa.