Two years ago we were doing a house scenario where the guests got to see the playroom of where the families child used to play with her toys. We had the room set up with dolls in a doll house (if you looked in the window of the doll house you saw bloody toys), then there were some stuffed animals, and other things that little girls play with. But her most favorite toy was a jack in the box (which I got off E-Bay for under ten bucks, and it worked). The guide would turn the crank on the box, and when it popped open, we had a large box decorated as a table (3 foot square), which had an actor pop out the top right beside the patrons. This scared the living bejesus out of them and forced them to the next scene.
Rolling Thunder Productions
A Tisket A Tasket, They Put Me In This Casket!!