If you read some of my posts, you may come to the conclusion that Knucklehead is self explanitory!
As with Mr. Pitbull's honest and candid explanation, I often put passion into things I believe strongly. That plus attempting (& frequently failing) to be succinct in written communication might mislead anyone reading into thinking I was angry or curt in my replies, so I tried to temper that with a silly screen name. I've been thinking about sizing a picture of Curly Howard for my portait, too.
What would be great is if I could get a nice photo of my Knucklehead Harley up, but that would require that I own one. Someday.