Gelalelope
A mammal with the general size and shape of a Hippopotamus, but with an unassuming, unamused expression on its face. The Gelalelope also has large wings resembling that of an eagle's, only they serve as balance organs more than anything. The Gelalelope is far too heavy to fly.
I saw a hippo on my last safari; only it wasn't a hippo. It was a Gelalelope.