When our family was on vacation in San Francisco, we happened to pass by a giant green screen sitting on the edge of the sidewalk by Pier 41. If you are not familiar with green screens, these giant green backgrounds are used by moviemakers to project real actors and actresses onto fake backgrounds, such as in spaceships and so forth. The kids and dad had experimented with a green screen app on the phone when we were at home but we really didn't have a proper green screen available. Thankfully we had some toy lightsabers (from Star Wars) in our backpack and the kids had a good time playing in front of the green screen while I filmed them with the app to insert special backgrounds. Then I plugged the video clips into the iMovie app (which has a nifty movie trailer template) and voila!