Fun story: Last time I flew, the scanner detected the surgical plate in my right shoulder. The TSA agent saw the diagram and put his hand on my left shoulder before letting me walk.
In October, I also triggered the machine for having a suspicious back.
The cause? I was in Hawaii, wearing a backpack. If you didn't know, their airports are mostly open-air. Of course, Hawaii is pretty warm and it was humid, so I was sweaty on my shoulders where the straps were.
I once went to the SLC airport with slightly damp braided hair. I went through the scanner. A TSA agent pulled me aside for a patdown. She did it quickly, sighed with relief, and said, "Oh, it's just your hair. It showed up on the scanner as a weapon."
