THIS MUST COUNT AS THE BEST MOTHER-IN-LAW JOKE! 

  A married couple was in a terrible accident where the man's face was
severely burned. The doctor told the husband that they couldn't graft
any skin from his body because he was too skinny.
  
  So the wife offered to donate some of her own skin. However, the only
skin on her body that the doctor felt was suitable would have to come
from her buttocks. The husband and wife agreed that they would tell no
one about where the Skin came from, and they requested that the doctor
also honor their secret.
  
  After all, this was a very delicate matter. After the surgery was
completed, everyone was astounded at the man's new face.  He looked more
handsome than he ever had before! All his friends and relatives just
went on and on about his youthful beauty!
  
  One day, he was alone with his wife, and he was overcome with emotion
at her sacrifice. He said, "Dear, I just want to thank you for
everything you did for me. How can I possibly repay you?"
  
  My darling," she replied, "I get all the thanks I need every time I
see your mother kiss you on the cheek."