Casey the Utterly impossible Horse by Anita Feagles, 13th Scholastic paperback printing, TW393, 1973, 80 pages. Illustrated by Dagmar Wilson.
DESCRIPTION:“When is a horse impossible? When he walks around in striped pajamas and a straw hat and glasses. When he wants to go to the drugstore for ice cream. When is a horse called Casey?” (from the back cover)