stop your cheap comments, bub -- we know which equine simpleton came first!
And, as Wikipedia explains:
A mule does not sound exactly like a donkey or a horse. Instead, a mule makes a sound that is similar to a donkey's but also has the whinnying characteristics of a horse (often starts with a whinny, ends in a hee-haw). Sometimes, mules whimper.
The Wiki also notes:
Mules today come in all shapes sizes and colors, from minis under 50 pounds to maxis over 1000 pounds, and in many different colors.
Well, I'm not quite there yet. . .
and Lydon ain't no Twiggy, neither!