Try mixing two or more animals together to create an animal. Research their physical features, the environment they do well in, senses, etc.
For example:
A cat-like creature with an alligator's tail and a bird's beak.
This creature would have cat-like instincts, but be able to swim underwater to to it's alligator tail (alligators are born to swim) and sing like a bird due to it's beak. Plus you could add anything else you want.
Another thing you could do is look up fantasy animals from video games and get inspired from them!
For worlds, you probably want to build a world that your animal could survive in.
No Man's Sky, a video-game, has endless biomes and worlds that you can take inspiration from for the climate and it's features.
You could also research about any known planets (doesn't have to be in our solar system) and mix two or more together, take aspects from one planet and give it to another, etc!
I hope these ideas helped you a bit :)