Penguins?

There is a mug that I have had for years with Naughty Penguins doing all sorts of things to each other. The weird Scandinavian claymation cartoon that Miles seems to love although I can't fully see the humour in it. And then of course the rash of recent movies and shows starting with March of the Penguins, which I have yet to see. One I did see was that Happy Feet movie, it was weird and disturbing. I really didn't like it, I think it is strange on a level that really doesn't need to be understood by anyone. I like penguins, at least I have never had a problem with them....but why penguins? Why not Hippopotamus (hippopotamus's?). They are cute, just not quite as small. I suppose penguin is easier to say and spell.