You're an idiot for still believing that deadmau5 actually gave some idiot like him his account credentials. He's a fake.
Here's a tip: When the server doesn't authorize the players that connect, you can log in with say "deadmau5" and the game will think it's deadmau5, so it would have a deadmau5 skin and head.
If you log in with the name "Notch" you'll get his skin and the Mojang cape. It's how the game works. Doing that isn't possible if the server has the authorize users option set to true.