Raskin is playing with sounds as well as pictures here and it's not hard to imagine an echoing chorus wherever her cumulative caper is read aloud. Who said whoo is easily answered and it's also evident as Sue drives along in her open car, acquiring more and more animal passengers, that "The honeydew snake said shoo!/ The chimp has a cold: A-choo!/ Two pigs said spitter-spatter;/ Gnitter-gnatter said the gnu" -- and so on through the remarks of the billy goat's ghost (boo), the kangaroo, the goose, the shrew, the cross-eyed owl (who said whoo) and the polka dot cow (moo). But the unanswered question throughout is who said chitter-chatter, and all but the chimp (remember his cold) scatter (saying PHEW!) when it turns out to be a skunk. "Moral: Words aren't everything." True. It's fun to spot each newcomer amid the changing foliage too.