I do bite my toenails. I'm abnormally flexible for someone of my height/build.
However, when I was younger I used to put both feet behind my head, walk around on my hands and open doors with my toes.
Now I can barely get one foot behind my head, but I can throw tennis balls with my feet (and the infamous "fingertoes" as they've been labeled)
Because you can't spell "Slaughter" without "Laughter"