There's the otherwise un-named cat in "Moving Pictures", who is essentially a feline Gaspode developing unwelcome sentience and colour vision; he manifests distinct characteristics of Tom (as in "and Jerry") and Sylvester from the cartoons. although not named ( a little romantic bit of me wonders if this is Maurice's first appearance in the books. No proof of this either.)
Although un-named, this cat has enough character to justify a mention here...