How to tell if someone is a boy

Mike was helping Anne get ready for bed and she was going to the bathroom. For some reason they were talking about how boys stand up and girls sit down to go to the bathroom. Anne informed Mike that he is a boy and that boys stand up to go to the bathroom. Mike was then teasing her and asking "Well then how do you know I am a boy?" --- Anne paused for a few seconds, put her hands into the air and said "because you don't have pretty clothes and you have a regular haircut." So... apparently the way you can tell someone is a boy is if their clothes are not pretty and their haircut is just "regular" :)