Betelgeuse is a variable red giant star. Remember the Peter Pan thing about the "second star to the right"? Well, Betegeuse is just to the right of that.
Betegeuse is the home star of the grey aliens. Because of its varying brightness, it gets dark enough on the grey alien planet so that it is totally depressing. That is why they roam the universe at those times, pranking everyone including humans on Earth. Not satisfied with 1,000-piece jigsaw puzzles, they like to cut up and reassemble humans that they kidnap. Don't knock it till you've tried it.