A three-year-old had been told several times to get ready for bed. The last time his mom told him, she was every insistent. His response was, "Yes, Sir!" Since he was talking to his mother (and she is a woman), it was not expected of him to call her "Sir".
"You would say, 'yes sir,' to a man, I am a lady, and you would say 'Yes Ma'am,' to a lady," Mom said. To quiz him on is lesson; she then asked him, "What would you say to Daddy?"
"Yes Sir!" was the reply
"Then what would you say to Mama?"
"Yes, Ma'am!" he proudly answered.
"Good boy! Now what would you say to Grandma?"
He lit up and said, "Can I have a cookie?"