It's testament either to the danceable rhythms of Mark Ronson and Bruno Mars' "Uptown Funk," or the fantastic dancing of early 20th century Hollywood or the editing skills of Nerd Fest UK who uploaded this video.
Or maybe it's a combination of all three.
Who knows? More importantly, who cares? Because it just works. There's Fred Astaire in a top hat (who is freaking amazing), there's front flips, there's Groucho Marx busting some leg shaking, and there's Rita Hayworth being effortless. Golden Age Hollywood knew how to move.
"My inspiration came from What's the Mashup? but I didn't manage 100!" says the YouTubers behind the video. "The idea was to do the same for movies from the Golden Age – meaning no title later than 1953 (although there is one at the end.) Oh, and none of these clips was sped up or slowed down."
If you switch on the subtitles you get the film names too, so you can go watch the whole movies if you're impressed with the moves.
And they are impressive moves.