Cute, furry little AL critters that are the main focus of the Creatures series.
The norns in Creatures 2 are notorious for refusing to eat food (although they'll happily attempt to 'eat weather'), running into walls continuously, and jumping in the oceans (they can't swim).
Creatures 3 norns tend to be more intelligent; none of the breeds sold by Creature Labs have an eating problem, and some people complain that they're unnaturally smart. Rumours of hard-coding their behaviour are false, though, afaik.