Cat is a supporting character in the novel The Last Unicorn and the Rankin/Bass film adaptation of the same name.
He is the second character to speak only in riddles, along with The Butterfly
He lives in Haggard's castle with her master and his adoptive son, Prince Lir. The king presumably owns the cat because he thought a pet could make him happy like his adoptive son, but to no avail. The cat is also the one who informs Molly about the skeleton that talks and can answer their question of where to find the Red Bull.
The cat is also aware that Amalthea is the Unicorn. What happens to the cat after the castle collapses is unknown, as he is not seen in the film after telling Molly about the Red Bull.