I don't really see how a hippo looks much like a horse. Maybe a horse with a weight disorder, I guess.

I vaguely recall that in ancient egyptian times and as late as the the classical greek era, there was a smaller species of hippopotamus, now extinct, indigenous to Egypt and parts of the middle east. Can anyone confirm or deny? Does the Bible include any references to hippopotami? (I know, ICLIU)

A bit of Ogden Nash:
We mock the hippopotamus
Because of how he looks to us,
But often, in a moment grim
I wonder how we look to him.
Peace! Peace! thou hippopotamus!
We really look al right to us,
As you, no doubt, delight the eye
Of other hippopotami.