I thought of this while I was walking through the mall today with parents taking their kids to see santa claus. I overheard one mother telling another how smart her child was who looked like he was about 6 or 7.

The opener is basically:
You: On average, what age do you think kids stop believing in santa claus
Her: 6,7,8 (her answer isn't really important)
You: Well it is usually somewhere between the age of 6 and 9 (you can go with whatever age you want)
Her: blah blah
you: ya, i was at the mall the other day and i overheard this woman telling her friend how smart her son was. He looked like he was about 7 or 8 years old. I really wanted to go up to the lady, and say "Listen, your son cannot be that smart he is 7 years old and still believes that a fat man flys around the entire world in one night in a sled, by reindeers, and on top of that is able to get down a chimney without a problem. (You can add in whatever you want here).

Depending on the girls reaction you can go a number of ways here. You can start by asking when she stopped believing in santa claus and use this as a way to neg her. If it turns out she's jewish you can also neg her that way, saying "I am really sorry that you don't get to celebrate Christmas, and on top of that it gets thrown in your face every where you go this time of year.

Interested in your opinions or modifications.