Check out the following clip if you're not familiar with the movie or the creature. It's got a large head, broad face, and 3 pairs of legs.
Like most other Hollywood movie monster/alien creatures, Woola is a mixture of other living things because, frankly, we're not all that creative...sigh. To me Woola is a mix of salamander, bulldog, and water bear...read on.
If you look at the video again you will see the shape of Woola's skull is clearly giant salamander (these live in Japan).
The inside of Woola's mouth is also VERY amphibian-esque. Amphibians (and many fishes) have teeth that line the jaws plus vomerine teeth. These are prickly extensions of the bones that make up the roof of the mouth. You can see both kinds on the upper jaw and roof of the mouth of a couple of kinds of salamanders.
The image below shows the inside of Woola's mouth, complete with vomerine teeth - but while amphibians have these teeth only on the roof of their mouths, Woola has them top and bottom:
What about the rest of Woola's body? It's eyes are WAY bigger than those of a salamander, and it has a profile that reminds me, at least, of a bulldog.
The flat face, the split jowls, protruding teeth, and apparently smiling face...pure bulldog, and pure Woola!
OK, the salamander/bulldog combo explains the head...what about the rest of the body?
To me the rest of the body resembles a microscopic animal called a "water bear" (a.k.a. Tardigrade). A tardigrade has four pairs of appendages and lives in water, even thin layers of water on mosses. Here's what tardigrades look like:
All you have to do is remove the last pair of legs, add a tail, a salamander skull, the modified face of a bulldog, leathery skin of a dinosaur, and you've got Woola!
Don't get me wrong...Woola rocks!