From Creatures Wikia
The Doozer (or Dooser, Encyclopaedia valeriensis) is a small brown critter present in Creatures 2. Normal Doozers' only purpose in life is to wander about the World, teaching Creatures words- either by randomly blurting them out or when pushed by the Hand or a Creature. They do not need to eat to survive and greatly dislike getting wet. If fallen into or dropped into water, they will attempt to leap out with an amusing shriek.
Doozers also have a purple-hued cousin that lives underground in the Incubator area. It supposedly eat stray tomatoes, and is not removeable from its natural habitat in the normal course of the game.
Doozers also appear in the PS1 game, Creatures: Raised in Space, but are referred to as "little animals". They do not teach your Norns vocab, but will become angry and attack them if kicked.