Easy mistake. A mule is a cross between a donkey and a horse. Mules are larger, stronger, more stubborn, hardier than donkeys, but less friendly and less tolerant.
The easiest way to tell a dolphin from a porpoise is that dolphins muzzles stick out like beaks.
The stubbornness of Mules is legendary.
Songs have probably been written about it.
Apparently, temperament can be passed on via DNA.
That’s how you get those hideous looking Bulldogs, who usually act very gently.