Growing up I listened to Daniel T. Johnston in High School thanks to Adam - with a happy smirk. I could never figure out if his music was tongue-in-cheek or if he was truly nuts. After checking out a biography of him from the library I realized he was brilliant and insane - like Dali or Blake. Years later Kurt Cobain discovered him.
Wesley Willis certainly is one of these - and if you need an irreverent Christmas tome that will get you through the next few weeks (don't go to Wal-Mart - that will help quite a bit..) listen to 'Kris Kringle was a Car Thief' on this site. And then listen to everything else when you have time. Unfortunately Willis and Whitley are no longer with us, but their music is.
