KyuuKyuu-kun (キュッキュ君, キュッキュくん, Kyukkyu-kun, named after the Japanese onomatopoeia of the rubbing noise, exact spelling varies) is an NPC that can be found next to the stairway area, reached from the Number World.
Kyuukyuu-kun is a tall, constantly smiling worm-like creature whose two black eyes have googly red pupils. Its body is multi-coloured, with red being the dominant colour. It is shown with a small arm that slightly rubs up and down the handrail of the stairs.
They can be accessed by stabbing an unhappy-looking Zippertile with the Knife effect. This method of entering The Stairway and the fact that the FACE event occurs when progressing further creates a certain discord with Kyuukyuu-kun being a smiling character.
KyuuKyuu-Kun rubs the pole faster if you equip the Knife effect, similarly to how other NPCs flee or move around when you equip the Knife. It also stops rubbing the handrail when you use the Stoplight on red.