Minecraft wiki entry for Donkey, associated text: If a player picks up leather dropped by an adult donkey, they receive the "Cow Tipper" achievement. This is due to the achievement being given when a player picks up any piece of leather instead of being given when killing a cow.
A player riding a donkey is dragged along if the donkey is being pulled by a lead, and can even be lifted up in the air in the same way.
Using commands, it is possible to make a donkey with no armor slot, but also no way to equip a chest.
In the Bedrock Edition, the donkey can be transported in a boat by riding the donkey and jumping into the boat then dismounting (leaving the donkey behind in the boat) and activating the boat from underneath/underwater. Attempting to activate the boat to pilot it from above results in the player being mounted on the donkey again rather than being placed inside the boat to pilot it.