An elderly couple walk into a doctor's office. The man tells the
   doctor, "Doctor, we want
   to have a baby." The doctor replies,"At your age I don't think it's
   possible, but I'll give
   you a jar, come back in a few days with a sperm sample." So the couple
   comes back a few
   days later.They give the doctor an empty jar. The doctor says,"I was
   afraid of this." The
   old man says,"No, it's not what you think. I tried it with my left
   hand. I tried it with my
   right hand. She tried it with her left hand. She tried it with her
   right hand. She tried it with
   her teeth in. She tried it with her teeth out. But we couldn't get the
   lid off the jar."