That is hilarious.
Also, since I'm already irretrievably creepy, I may as well say, alternatively to the XKCD dating rule there's Dan Savage's "campsite rule" for dating younger people. "If you date someone substantially younger than you, you have a responsibility to them to ensure that your relationship leaves the younger party in better shape emotionally and mentally than when you met them." (Ideally this rule would apply to any relationship obviously, just when one person is quite a bit younger there's a greater responsibility on the part of the older person. Also obviously there is still some common sense involved about how young is too young, just no hard and fast rules. Aside from applicable laws obviously.)