They were all killed by the fire breathing dragon. That changed when Shrek and Donkey tried. When they were about to get eaten by the dragon Donkey started complimenting it and found out it was a girl dragon. Donkey starts a relationship in the later movies with the dragon.
Donkey/Mule A donkey is a donkey A horse is a horse And a mule is half donkey (sire), half horse (dam) of course, of course, of course A donkey is a donkey (no need to explain there!) and a mule is the offspring of a female horse and a male donkey.
Ask him, if it happens to be a magical talking donkey (as in the movie Shrek). Alternatively, check the condition of the teeth. Donkeys, like horses, are grazing animals, constantly chewing on grass, and this gradually wears down the teeth as they age.