Make a video in 15s or make a 15s long video?
I'd suggest some video sleight of hand that gets peoples' attention.
Morph one thing into another. Get MorphX for free to do this.
Make up a very short story. Bored kid doing homework unfolds a magic box, crawls into it. Camera shifts to a playground. Kid crawls out of the box and runs to play. Time permitting he goes home the same way and mother comes in and is surprised to see grass stains on his pants.
There are endless variations on that theme. Do like they did in the matrix. Every time they opened a door it led somewhere else.
Use a digital camera on a tripod to make a time lapse movie. Figure 30 shots per second. You need 450 pictures. Figure out a plan. Have someone move a tiny bit along a path then take a picture. Rinse and repeat. Later use GraphicConverter or similar to convert the photos to a movie. You can get all sorts of strange effects this way. By moving just a little at a time you can appear to ice-skate across the living room floor. There was a really funny movie from ages ago made like this. People were all sliding down the street as if they were driving to work and such but without their cars. Just the bodies. Set the camera to 640x480 resolution.
Same idea as above but use little Lego toys or modeling clay to make a claymation movie.
The hard part of all this is to think of the story. The story is what makes all the effects hang together. If you have a really good story in mind viewers will forgive all sorts of weakness in the effects.
