This trick utilizes a prop head that triggers to life upon opening the trunk. The trick requires you to have an old trunk (found at garage sales, flea markets, import shops, second-hand stores, or attics). You'll also need a nasty looking head prop. The most effective choice would be to use a corpse or skeleton head prop that also has the shoulder attached. You can also use a plastic skull model or Styrofoam wig stand with a mask.
To build the device pictured you’ll need a 12" section of 1" or larger dowel rod and a section of 1.5" PVC pipe 14" long (or enough to stand the head completely out of the trunk once the lid is opened). You’ll also need an 18” section of 2"x12" board, one 6" section of 2"x12" board, (2) sections of 2" x 4" x 4" board, (2) 2" x 4" x 3" sections of board, a latch clasp used with a pad lock, a 1.5" PVC "T" fitting, and a wide rubber band about 5"-6" long.The PVC pipe connects the head to the "T" fitting. The dowel rod is used to hinge the PVC pipe to the base supported by side bracket blocks. The end brace board connects the rubber band to the PVC pipe to act like a spring. See diagram for construction details.The head is latched down in the spring set position, with the unit resting on the floor inside the trunk. The lock pin is inserted and the other end clipped to the inside of the lid. This can only be set when the lid is almost closed, since the string is just long enough to reach so the pin is released when the lid is fully opened. Pulling out the pin pops the latch open (from upward force of PVC pipe), and the head pops out of the trunk.
This device can also be mounted to a wall or door with a window.
A similar effect can be achieved by building a dummy that swings open window shutters and pops out at guests as they pass in a hallway. The dummy has fake hands and arms attached to the inside door handles, a stuffed torso, and a wig stand with full head mask or fake severed head. The mechanism is operated from behind the figure by a helper.