I sort of happened to me once. I created an image and posted it eons ago (2006), got a few laughs, then promptly forgot about it. A few years later, like five years after the fact, I was following along with a PowerPoint presentation at some work thing and there was my image in the middle of it. Apparently the image had become an office favourite and ended up spawning a bunch of similar images, then t-shirts, coffee mugs, posters, all sorts of things. I started seeing the image in things like the documentation for Google Charts, and in other presentations. It was weird. The image blew up and I had zero idea it had happened. It spread via Boing Boing and Wil Wheaton, believe it or not.
I can only take credit for the image itself, as the joke itself came from a magazine I had read at a dentists office.
So yeah, I can totally see it happening, ‘cause it borderline-happened to me.