fictional animal vs creature

fictional animal and creature both are nouns.

Word	Noun	Adjective	Verb	Adverb
fictional animal	Yes	No	No	No
creature	Yes	No	No	No

As nouns, creature is a hypernym of fictional animal; that is, creature is a word with a broader meaning than fictional animal:

fictional animal: animals that exist only in fiction (usually in children's stories)
creature: a living organism characterized by voluntary movement

Other hypernyms of fictional animal include animal, animate being, beast, brute, fauna.

fictional animal (noun)	creature (noun)
animals that exist only in fiction (usually in children's stories)	a living organism characterized by voluntary movement
	a living being
	a person who is controlled by others and is used to perform unpleasant or dishonest tasks for someone else