Not only kind, funny, crazy outgoing, deeply loyal, loving, and a fantastic singer, but also a good performer in more ways than one. He will help you with advice and comfort when you need it, and back off to give you time to think and make your own decisions after he's had his say. A person who knows who he is, what he wants, and how to get along with the rest of the world (unless a member of said world makes themselves his problem). He knows his weaknesses, is articulate about his thoughts and feelings in appropriate situations, and pretty much has everyone else in his life figured out.
Warning to the "normal", shy, or just introverts: If you befriend a Donn, he is highly likely to burst into spontaneous bits of song or vocal imitations at any given moment, no matter where you are. This is what we meant by "crazy outgoing" in the preceding paragraph. Deal with potential embarrassment as you see fit.
Person 1. "Did you see that guy singing from the second floor in the mall?"
Person 2. "Yep. Must be a Donn."
Person 1. "I went to Walgreens with Donn the other day and he put on Cartman's voice because the cashier's name tag said Kyle..."
Person 2. "Well, what did you expect?"