They can ride in your shoulder. Having a monkey while sailing in your pirate ship is strangely satisfying. 😎

If you put them on wandering they'll pick up berries. When you put it on your shoulder it throws poop at your enemy and the poop does damage and slows down the target

If you put stuff in its inventory like eggs or materials and then put it on your shoulder it will weigh less than it would with the items in your own inventory making it perfect to cook kibble fast

Good for Pvp severs if you can tame high level preferable 100+ as they can unlock doors from entering a open window