I've blacked their eyes out because you might be that Internet paedophile we hear about so often.
OK, so it's pretty obvious what they did when they posed for this: they got down on a shiny floor, rested on their elbows, and smiled. I've explained this to my mother, and she understands perfectly well what they did and that the lower half of the picture is a reflection. However, she doesn't see it that way at all. This is what she sees:
I've shown her with a mirror what's going on, I've turned it upside-down and shown her, I've covered up various parts and rotated it, but she can't see those reflected arms as anything other than legs.
Oh well, that's my mother. She knows, because she's been told often enough, that 1 times 1 is 1, but she still can't see why it isn't 2.
(No, that isn't a metaphor — she really does think 1 times 1 ought to be 2..!).