Donkey

A donkey or mule is a creature found or mentioned throughout the wastelands.

Background
Some mules or donkeys survived the war, serving as labor on farms. A man named Irwin shares information with the Vault Dweller about his donkey, Pugsley, who was killed by raiders.

Mentions

 * The Courier can tell Diane that they are not interested in being a drug mule.
 * The description for the Strong Back perk in Fallout 4 mentions a pack mule.
 * A mule is referenced in the World of Refreshment terminal entries as part of an advertisement for Nuka-Cola Wild.
 * As a companion, Codsworth mentions that it has not seen an airplane in "donkey's years."
 * Christopher Wright tells the Chosen One that his mom is "as blind as a mule."
 * Silver Rush doorman Simon tells the Courier that plasma weapons fire "as slow as a mule, but with a kick to match."

Appearances
A donkey appears Donkeys and mules are mentioned in Fallout: New Vegas, Fallout 4, and its Nuka-World add-on.

Behind the scenes
According to Chris Avellone, Pugsley's existence in Fallout was a discrepancy.