Night of the living dummy 2 - R. L. Stine

They're baa-ack! Make way for the bestselling children's series of
all time! With a fresh new look, GOOSEBUMPS is set to scare a whole
new generation of kids. So reader beware--you're in for a scare!
He's still walking.
He's still stalking.
Amy's ventriloquist dummy, Dennis, keeps losing his head -- for real.
So Amy begs her family for a new dummy. That's when her dad
finds Slappy in a local pawnshop. Slappy's kind of ugly, but at least
his head stays on! And besides, Amy's having fun practising
her new routine. It's like this dummy knows what she's thinking.
Like he can move on his own. And it's great - until Slappy starts
a routine of his own. A nasty, horrible routine. And Amy can't control
him...