Even if it's been years since you burned your own mix CD, you probably still have a few jewel cases lying around. If you also happen to have a ruler, scissors, tape, graph paper, and can get your hands on a glass cutter, you have the tools you need to make holograms with your smart phone.
YouTuber Mrwhosetheboss has put together a simple tutorial, breaking down how to make a homemade hologram generator. Surprisingly, it's as simple as cutting up plastic and taping it together. There's just one catch: in order to make the illusion work, you need to find special videos that show the same image four times. Luckily, Mrwhosetheboss helpfully provides a video to use. The results are stunning: