The Terrible Plop by Ursula Dubosarsky, pictures by Andrew Joyner is one of my choice apple books for the season.
These little bunnies are down by the river munching on carrots and chocolate cake when they hear this terrible plop. They run terrified through the forest and all the other animals start running away too, until they come to the bear. The bear makes the smallest bunny take him back to the spot because he doesn't believe that there is anything any scarier than him.
This story has a riot of rhyming coupled with mixed-media cartoon illustrations. I love the mixture of animals that would never be in the same forest together. The mixture of 'real' items for the bear's fur, and the chocolate cake add to the illustrations. There is terrific details of the animals expressions.
I like to use this story the best with Kindergarteners and up. Students are encouraged to discuss times that they have been afraid of something they hear or see when they don't know what it is. The children really like to be in on the joke with you. I also have the kids make the terrible 'PLOP' sound with me, everytime it comes up in the story; I draw out 'theeeee terrribllllle PLOP!' and have them say it with me as I raise my hand and then slap it down on my leg. This is already a classic for me.