Everything In Zootopia Is Moving All The Time
What most people don't realize about animated movies is that most of the frame isn't actually animated. There's usually a single static background with a few animated cells on top of them -- this is clear in low-budget TV cartoons, where the moving frames tend to have a slightly different color from the immobile background, but it's more cleverly hidden in big-budget Disney movies because of that aforementioned big budget. The reason they don't animate the entire frame is, of course, because that would be insanely fucking time-consuming. It's way easier to have one still picture while Batman or Scooby-Doo conduct their slapstick antics on an entirely different layer.
Or both at the same time, I guess.
Unless you're making Zootopia, in which case -- for the first time in Disney history -- absolutely everything is moving. And by "everything" I mean, in fact, "all the things." Every shadow shimmers. Every car sputters. Every strand of hair twitches and wafts in the wind. All 30,000 leaves on that tree are moving, thanks to technology developed just for this movie.
Finally, a film can recreate the nightmarishly overstimulating reality of living in a real city.