Minecraft's latest snapshot update, 19w07a, allows players to create animated paintings, paving the way for widescreen TVs showing full-length films.
The update breaks paintings up into individual textures, and players have been using that to show video footage of varying quality. The smoothest example is this one from user destruc7i0n, which I've clipped above. They were able to stitch together different paintings to show a high-quality copy of the Gravity Falls intro.
You can replicate it yourself by downloading the files in the post. Basically you just place the paintings and apply a resource pack. A word of warning: it's 500MB, and having multiple animated paintings on a server will certainly cause a bit of lag.
Another user, ShaneH7646, put the entire Bee Movie into the game, because why not? It's a bit like watching one of those picture flip books—it's about 1600 frames, and another user calculated the entire Bee Movie at 30 FPS is 171,000 frames (which could be the answer to a very niche pub quiz question), but you get the idea.
My favourite use of it is the most basic: user hopeabandoner created a painting that shows a very pixelated version of YouTube, with a Minecraft video playing on screen. It reminds me a bit of my old laptop.
If you want to make your own, there's a decent bit of advice in this thread. Now all we need is some in-game popcorn and we'll be set.