A work chum of my old man was bemoaning the fact that his eldest had sussed Santa was actually mummy & daddy and had leaked that little tidbit to his young brother.
My dad asked for a list of what they word be getting and what his chums phone number was. Cue Christmas day and older offspring was reportedly wide eyed when he got a personal call off Santa, "just checking" that his (correctly identified) list of pressies had been safely delivered.
I even had the immense satisfaction of doing much the same for one of my own work chums, many years later.
Anon cos, well, I really AM Santa.
Try it yourselves if you can. Made my day, it did.