Windows used to secretly use green screens to render videos, which is how you could trick MS Paint into becoming a video player

Never gonna Paint you up.

If you opened up the ol' Windows Media player back in the 95, 98 or XP days, brace yourself for a mild shock: it was lying to you.

And by lying, well, what I really mean is rendering video somewhere other than inside the actual window that was open on your desktop—sort of a parallel plane of existence to the desktop you were actually looking at—before sneakily porting it over.