Fat heads

I picked up my Gwynn Valley baseball cap the other day and found that the sizing was adjusted for a head bigger than my own, which could only mean one thing:  Mary, she of the mighty noggin.  I jokingly started accusing her of borrowing it and adjusting the size, when Graham rose to her defense, saying that my head is bigger than hers.  Well, both Mary and I corrected him on the one, but he came back at us:  "But your head is much fatter."