It's been present the whole time, but the weird sexual dimorphism between the males and females of the different species just bugs me more and more as this series continues.
All the guys are cartoonish semi-anthro versions of their animal, and all the girls are basically human chicks with animal ears, a tail, and maybe an odd nose. I get why, but it still seems really weird. It also raises some questions about mating, particularly for species like the naked mole rats, where the males barely come up to the ankles of the only female we've seen, or how degenerate it would look for any of more animalistic-looking males to score with females of supposedly their own species.