Bear and Bunny by Daniel Pinkwater illustrated by Will Hillenbrand

Bear and Bunny are best friends but feel the need for a pet.  They search the forest and come upon a "kitty" (really a frog) in a tree and adopt him for a pet.  The fact they think the frog is a kitty made my kindergartner belly-laugh!
Mr. Hillenbrand's illustrations, of course, are adorable.
*Borrowed from the library.