I’ve seen Zootopia (2016) and Zootopia 2 (2025).
The plot for Zootopia 2 was about how all of the reptiles, who were sentient in this world like the mammals, had been evicted from Zootopia. Once you saw this movie, you retrospectively noticed how all of the animals in the first movie were mammals. I’ll admit I hadn’t noticed this in 2016 and I don’t feel it was widely noted.
Was this deliberate? Did the people making the first movie already have ideas for the sequel and intentionally leave out the reptiles? Or did they just make the first movie with all mammals for other reasons and then realize the lack of reptiles could be the basis for a sequel?