Muley

Muley is a tame mule who lives in the town of Stal. His horse mother (name unknown) abandoned his donkey father, Donkey, as soon as Muley was born.

He was raised by his single father and Max, and when he was all grown up, his father retired.

 Trivia 

His grandparents had a lack of imagination, so they named his father Donkey, simply due to the fact he was a donkey. His father was encouraged by his parents to also straight-up ignore creativity, and they abused Donkey physically and verbally. Due to this terrible parenting, Donkey never learned how to be creative with naming conventions, so when he had a mule son, he named him Muley.

At least that was a little more creative with that "Y" at the end, eh?