Bob goes to the doctor with a bump on his forehead.

He says to the doctor, "I got this red lump. What do you think?"
The doc runs a few tests and comes back looking flabbergasted.
"Bob this is incredible..."
"What is it?! Am I going to be okay?"
"It's like a ufo. I've only ever read about it but you never actually see one, this is amazing!"
Bob is getting more nervous
"Give it to me straight" he says
"Well... There is a penis growing from your head"
"A penis?! Cut it off!"
" I can't it's already become a part of your brain, the operation would kill you" the doc explains.
Bob asks "you mean to tell me every morning when I wake up and look in the mirror I'm going to see a penis growing from my forehead...?"
The doc laughs
"Of course not! The balls will cover your eyes!"

Bada bing, my favorite joke courtesy of car talk.