From Boing Boing, an endearing tale of a South African Pet House-Hippo:
(Warning: it goes from cute, to unbearably cute, to slightly creepy, to cute again.)
This is the same basic process in which humans have domesticated all animals - Jessica (though tame) is still wild, and potentially dangerous. Hippos kill more people in Africa than sharks, lions, and just about every other animal. But after a few dozen generations of similar treatment, it would be entirely possible to have permanently domesticated hippos. The domestic cow, which descended from the mighty aurochs, was surely much more dangerous to domesticate, weighing twice the weight of modern cattle.
So who's up for domesticated hippos? Can we have a pygmy version?