You buy and merge animal's DNA to get different animals. if you have a duplicated animal, click on them to remove them (useful after getting hedgehog and pufferfish).
For the ones that don't know what the animal (or critter) is on the landscape's side. That's a fluffy pony. It was originally gonna be a animal on the landscape. The beast sleeping (which is the landscape) was originally gonna be woken up by a animal (which is the fluffy pony)