I second Sandy Berman's December 17, 2008 letter to the Cataloging Policy & Support Office suggesting LIBRARY CATS as a subject heading. He cites an AP review of Dewey, the Small-Town Library Cat Who Touched the World by Vicki Myron and Bret Witter (which I notice, btw is available in Polish!) as warrant.
Quoting Sr. Berman:
"It's time to establish a new subject heading for
"LIBRARY CATS
"UF Cats in libraries
"Cats, Library
"Library pet cats
"Pet library cats
"BT Cats as pets, Libraries"
I bet many of my fellow lolbrarians would agree.