If you've spent much time around picture books (most recently, The Invitation, p. 436, J-108), you know whose birthday it is when bumbling Bob Bear gets an invitation to a party--namely, his. The situation is such a staple now, in fact, that the author doesn't even bother to try to explain: 1) how it is that everyone but Bob knows it's his birthday; 2) why an invitation is delivered to him; 3) where the invitation tells him to go. He starts out with a pot of honey as a present; wonders ""Who would have a birthday in the middle of winter?"" (the book's one bright line); and has various minor misadventures before reaching his own door (""Why, that's my cabin!"") encased--because he has tripped--in a ball of snow. The whole thing seems to be rigged for that grand entrance, with the other animals waiting--and maybe it was.