Anti-Gravity Mirror
It's all done with mirrors.
A reflection of your right side can appear to be your left side. With this Snack, you can appear to perform many gravity-defying stunts.

(with stand:15 minutes or less: without: 5 minutes or less)

You can make a stand for the mirror from a length of 2 x 4 inch wood. Use a router to cut a groove that is just wide enough to slip the mirror into. To help stabilize the mirror, you can nail some scrap wood to the ends of the board. You can also hold the mirror in a vertical position using ring stands and clamps, or just with your hands. An assistant might be of help here.

(15 minutes or more)

Stand the mirror on the floor or on a sturdy table. Put one leg on each side of the mirror. Shift your weight to the foot behind the mirror. Lift your other leg and move it repeatedly toward and away from the mirror. To an observer, you'll appear to be flying. If you use this Snack as a demonstration, you can make the effect more dramatic by covering the mirror with a cloth, climbing onto the table, straddling the mirror, and then dropping the cloth as you "take off."

A person standing with the edge of a large mirror bisecting his or her body will appear whole to a person who's watching. To the observer, the mirror image of the left half of a person looks exactly like the real right half. Or if the person is standing on the opposite end of the mirror, the right half looks like the real left half. The person looks whole because the human body is symmetrical. The observer's brain is tricked into believing that an image of your right side is really your left side. So just straddle the mirror, raise one leg, and you'll fly!

Try this out in department stores that have full-length mirrors available. If your school has a dance room with a mirrored wall and a doorway cut into it, you may be able to use it. With these full mirrors, stand at the edge of the doorway so that just half of your body is being reflected. This will be an even more convincing flight.
The cars that floated across the desert in the movie Star Wars each had a full-length mirror attached along their lower edge, hiding the wheels. A camera pointed at a car saw a view of reflected sand and shadow in the mirror. That is how the cars appeared to float above the sand.