The first animal was an Axolotl; it's a kind of amphibian
that lives in water and has gills like a fish.
Recently, thanks to new scientific measures, scientists have discovered the first ever living animal to exist was an ocean-drifting comb jelly. In other words, a creature in the form of protoplasm.
Before you get confused, the comb jelly is not a jellyfish, but it does have similarities to a jellyfish.
Previously, it was thought that sponges were the first animal to exist, but we now know that isn't true. Evolution evidence found that comb jellies were here first and that sponges de-evolved from a form of jelly-fied animal.
And yes, you read the word "de-evolved", not "evolved".
Many examples of fossilised comb jelly creatures are hundreds of
years older than fossils of sponges. Further indicating that the
jelly appeared first.