Guu

Guu's stomach is a world, filled with buildings, hundred legged cats, and two nice, young people that have been trapped there for ages (but apparently don't mind their predicament).

Other than Hare, no character seems to be aware of Guu's strange nature (or for that matter the bizarre circumstances surrounding everything else in the series).

The weird events that occur because of her are only ever acknowledged by Hare. Everyone who is eaten by Guu, only to be spat out later, dismisses what happened as a dream. Hare even dismisses his first time in Guu's Stomach but is quickly proved wrong.

There are other strange things Guu can do, which defy the laws of physics, logic, and reality, such as (but not limited to) superhuman strength, elongate her body parts, breathe underwater, teleport, time travel, cause people to switch bodies, read minds, cause disco music to play suddenly, switch her face (from a cute face to a weird face), transform into an older version of herself, transform into a giant kaiju monster version of herself, incite mental breakdowns in Hare, though the latter is more of a talent than an actual power and can connect anything to video game controllers and play around with it (even peoples minds).

In one scene Guu hints towards being programmed to do what she does.