Instructions
Choose a box where you would like to place your Jack-in-the-box. This can be of any size, though a smaller box typically works better than a large one. You must consider the size of the Jack-in-the-box that will emerge from the box if it is very large. You can find boxes at kit stores or online at sites such as Hand Crank Toys (see Resources below).
Hinge the lid of the box or choose a box that is already hinged.
Drill a hole in the side of the box and install a crank-operated music box. A crank-operated music box can be found in a craft store or stores that sell kits. You can also find these at Hand Crank Toys, a place that sells custom Jack-in-the-box parts. These kits will have the necessary latches that release at the appropriate time. Follow the kit's directions for installing.
Install a latch on the inside of the lid, and install an arm that will catch on the latch. The other end of the arm should be attached to the crank so that it will release the latch when a certain moment of the music is reached.
Affix a Jack-in-the-box of your choice onto a spring, and secure the other end of the spring to the bottom of the box.
Finish the outside of the box in any way that you like.
Close the lid, give the box to some unsuspecting person, and enjoy.