R.L. Stine 
I Am Slappy’s Evil Twin [EPUB ebook] 

In this spinoff to the New York Times-bestselling Goosebumps series, two mannequin dolls, props from a horror movie, come to life and terrify a tween boy.Luke Harrison’s dad makes horror films. 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?