The Pinball metaroom in Creatures 3 is a rather strange hidden room with no obvious purpose, other than to appear like a pinball machine. The Toilet Control device is inside this room, which makes certain critters' waste visible.
It has been said that the original developers intended to make a game with this, as with the Grendel Invaders game, but whether this is true or not is a mystery. Another possibility is that it was used to test the physics portion of the Creatures Evolution Engine while in development.
Open up the CAOS Command Line with SHIFT+CTRL+C and type in:
meta 5 1 1 1