Boo to You!

"Friendly Halloween characters visit one another to deliver Halloween treats without being seen. When each door is opened, it reveals a different character being “booed,” while the giver of the BOO is hidden behind the door flap. On the next spread, the character who has been booed goes on to boo another friend, and so on. The final spread reveals all 4 characters, who have previously been booed, as they head to one final door with a mirror behind it. Guess who they boo?"--Amazon.com.