On Christmas Eve, two curious children visit the North Pole to deliver a letter to Santa. But where is he? Will they find him before he takes off in his sleigh? Lift the flaps in this knock-knock joke book and find out. This bestselling series has sold over half a million copies and is now refreshed with vibrant new art from Steve Björkman. Knock, knock! Who’s there? Sandy. Sandy who? Sandy Claus is who we're looking for. Follow the children through the busy workshop where elves tinker and wrap toys, through the reindeer stables, and finally to Santa's house. There are plenty of surprises and laughs in store.