The Beast of Monsieur Racine by Tomi Ungerer

Monsieur Racine wakes up one day to find his precious pear tree looted of all the award-winning fruit. When he discovers that the culprit is funny-looking beast, his anger gives way to curiosity and two become friends. But the beast is not quite what it seems, eventually it comes apart-literally to show itself to be no beast at all, but the two playful children from next door, covered with skins and rags.