I love to surprise a child with something their parents have told me about them. A 10 year old boy wanted a motor scooter for Christmas but his mother told me he that had an accident with his go-cart, and I told her I would take care of that.
So when it was his turn to sit on Santa's knee, and I asked him what he wanted for Christmas. He told me he wanted a scooter. I gave him his gift and we got pictures taken. Before I let him go, I told him the story about a little boy that had an accident with his go-cart. He looked at me and said "How did you know about that?" then he said "Oh, because you are Santa!" I told him that he needed to wait another year or two before he could get a scooter.