An Arizona Highway Patrol officer stops a Harley for traveling faster than the posted speed limit:
He asks the old biker his name.
“Fred.” He replies.

“Fred what?” The officer asks.
“Just Fred.” The old man responds.

The officer is in a good mood, thinks he might just give the old biker a break and write him out a warning instead of a ticket.

The officer then presses him for the last name.
The old man tells him that he used to have a last name, but lost it.

The officer thinks that he has a nut case on his hands but plays along with it.
“Tell me, Fred, how did you lose your last name?’
The old biker replies.
“It’s a long story, so stay with me. I was born Fred Johnson. I studied hard and got good grades. When I got older, I realized that I wanted to be a doctor. I went through college, medical school, internship, and residency, and finally got my degree, so I was Fred Johnson, MD.