Ann, Jan and Fanny were 3 sisters, one night Ann and Jan had dates. Their 2 suitors took a look at Ann and Jan's feet and said " look at your feet, they're tiny" Ann and Jan replied..." you should see our Fanny's, they're huge"!!!
Reminds me of that immortal line from the Fanny Craddock cookery programme years ago when johnny said "Goodbye, and may all your doughnuts turn out like Fanny's"