I am Slappy's evil twin - R. L. Stine

The evil dummy comes to life to tell his own twisted tales and scary
stories!
Luke Harrison's dad makes horror movies. It's very fun to be around
such scary stuff - especially when you have your own monster museum
at home. But when two ventriloquist dummies join the collection,
things get real creepy. Real-life creepy! Slappy and Snappy
can walk and talk on their own. And they can make you scream on
their own. They have a plan to make everyone's lives miserable. Will
Luke be able to stop this terrible twin twosome?