"Night of the Living Dummy" by R.L. Stine is about twin girls who each have a ventriloquist dummy. During the course of this horror story, one of the dummies comes to life and starts terrorizing the girls.
"Night of the Living Dummy" starts with twins Lindy and Kris Powell deciding to explore a house under construction. Lindy finds a ventriloquist dummy. She decides to keep him and name him Slappy.
Lindy starts having success entertaining with Slappy, which makes Kris jealous. The problem is exacerbated by the fact that Slappy is mean to Kris, supposedly meaning that Lindy is making the dummy do mean things like slap her sister.
The girls' father buys Kris her own ventriloquist dummy at a pawn shop. Kris names the toy Mr. Wood and competes with her sister over whose dummy and ventriloquism skills are better.
Late one night, the girls walk into their room to find Mr. Wood seemingly strangling Slappy. Even later, they find Mr. Wood in the kitchen supposedly eating a mess of food from the refrigerator. Kris is afraid of the dummies until Lindy confesses that she's responsible for their actions.
Kris finds a slip of paper in Mr. Wood's pocket with strange writing. She recites the words, and the dummy comes to life. It terrorizes the girls, neighbors and schoolmates until the girls throw it under a steamroller.