I'm surprised no one added it to the Chronology topic, but at the same time I now struggle to recall the details and find it.
I was pretty certain that Solid started it, in '09 or '10, and I think in either Gallery or Creativty.
As I recall, he had some obviously photoshopped image, but said it was real because it had a pine tree in it.
It was just really funny, and it became a joke that if your picture had a pine tree in it then it was authentic. And then it was used the opposite way, that is that an image without a pine tree in it could potentially be fake.
That's how I recall it at least. I'm not sure how much is true, and I have no idea why I think it was Solid.