Q. There are so many books with imaginary characters, but both the Imaginary playmates and the Fantasy subject headings are hardly ever seen on records. Why is this?
Welcome to the world of children's literature. Real woolly mammoths, as well as dragons, elephants, and dinosaurs appear all the time in children's books. Most of these characters can't exist but in children's literature real (even extinct) animals appear regularly and we don't add the heading Imaginary playmates to those books. CYAC decided years ago NOT to put Fantasy on most types of books, even though they may be clearly fantastic. CYAC based this decision on the fact that every other book we catalog would need the Fantasy and Imaginary playmates headings, as our literature regularly features visiting dinosaurs, magical tree houses, and anteaters wearing suspenders.
Generally, we restrict the use of the heading Fantasy to novels set in fantastic worlds, or alternate worlds. The heading IS used on high fantasy.