Which species get human forms?

[Ika Musume 54]

Obviously ponies and sirens do, and then diamond dogs do but apparently they seem... different. Spike was made into a dog, but dragons are just as sentient as ponies in Equestria. What about cows? Critters appear to just be critters, but those might not even be counterparts at all.

[Rosy Moonlight 369]

What species that turns into humans in the Human World seems to depend on plot and marketing.

[nightshroud96 124]

At this point, it seems that everyone except dragons get to be humans.