In Majora's Mask, you can take a quest to protect Romani Ranch from aliens. Unlike the usual goblin-types with swords and shields--you know, standard high fantasy stuff--you have to stop floating, ghost-like enemies with light beams who are trying to abduct cows. So, of course, someone decided to bring that vibe back in Tears of the Kingdom with a fully-functioning UFO and Majora's iconic Mask.
"if you know, you know", Katsan84 said on the TOTK subreddit, attaching a video of them running around half-naked with Majora's Mask as a UFO shoots a light beam at a farm full of cows. The contraption spins in a circle as it hovers overhead, but of course, there are no alien pilots or enemies to fight off. Unless you count the cows.
Seeing a giant UFO in TOTK had players wanting to try it for themselves, so Katsan84 put together a guide shortly after. Essentially, you put together an octagon with metal rails, attach two in the middle, add four fans at an angle on each corner, build up four ramps to the centre, and then place a downward-facing mirror and a beam emitter in the middle. On top, place another downward-facing mirror, then whack it and watch it spin as it shoots a beam of light. Of course, it works best at night.
If you want to put this together, you'll need to head over to the Right Leg Depot underground. The metal planks are rails that you can pick up there, but once you've done that, you can use the auto-build function to take your UFO wherever you want. That also means being able to build it above ground, but something about aliens getting stuck in a giant cavern is pretty funny, so if you just fancy staying in the depths, have at it.
If you want the Majora's Mask to complete the look, you can pick it up by completing the Lynel challenge at the Floating Coliseum in the depths.
Someone in the comments suggested that you could pair this UFO build with the ascend ability to shoot up through the beam into the sky, essentially abducting yourself. There's no practical reason to it, just a cool alien aesthetic, but if you're putting together a little TOTK video, why not? Others suggested adding bright bloom seeds to make the UFO even brighter, rather than just relying on the centre beam, since most depictions of UFOs have them lighting up the night sky. You can always try that yourself, since it's pretty simple to put together.