If you sit on the lap of someone dressed as Santa Claus and ask for something, you'll get it.
I realize that I held this unexamined belief around 12 years ago. I was a children's librarian, and it was the day of the library's Santa Visit. One of our maintenance guys was Santa, and they were testing the camera by taking pictures with the staff on Santa's lap. When Santa asked what I wanted, I was about to reel off my standard joking answer -- "Three bedroom house with attached two car garage" -- when it hit me that the only way I was going to get one of those was if a relative died, and I was struck dumb, suddenly afraid of uttering the selfish curse that would kill off a loved one.
When I was a teenager, I knew prayer didn't work. And I knew long before that that there was no magic. I've known practically all my life that the men dressed up as Santa weren't the real Santa. But somehow, I'd kept believing that the universe will give you what you want if you ask a Santa for it.