KyuuKyuu-kun (named after the Japanese onomatopoeia of the rubbing noise, exact spelling varies) is a non-NPC character that can be found in the Stairway, which can be reached from the Number World.
He is often thought to be an example of phallic imagery present in Yume Nikki, as many have speculated that KyuuKyuu-kun resembles an erect penis or, according to some, a colorful dildo. Kyuukyuu-kun is accessed by stabbing an unhappy-looking zipper tile with the Knife effect. The zipper tile is located in the southeast corner of the Numbers world, to the right of the door with 0's and 1's in front of it.
The zipper tile's expression changes randomly. If it's in the normal state, the player is advised to wake up and return until it changes. Theories regarding Madotsuki's past have arose from the zipper entrance. Some believe that the entrance through the zipper symbolizes rape or molestation. Some also believe that the zipper represents Madotsuki's shame for being transgendered or identifying as a male, due to the subtle phallic imagery. KyuuKyuu-Kun rubs the pole faster if you use the knife effect and slower with the cat effect equipped. Reaction to Kyuukyuu-kun is varied; some players find him adorable and others find him unnerving. It's as if he is wearing a mask, has a fake face, or he is too busy and perfectly happy with his pole to notice anything else. Some fans believe that he may be the rapist of Madotsuki. As with using the Knife effect, he goes faster; it is common in rape: when the victim tries to escape, rapist will get more aggressive, akin to going "faster", just as KyuuKyuu-kun does.
"The stare of KyuuKyuu-kun is that of a monster that doesn't know whats going on, the kind of monster that might hug you, and might hug you too hard, and not know when to stop" -Ok Gold, on Uboachan.