Hypothetically, I had a friend who went deer hunting a lot, and I knew where his game camera was. I and some other guys played around in front of it doing stupid shit so he'd get a laugh next time he checked the camera. We noticed that one of the pics looked kinda creepy, so we took the SD card out and mildly shopped it to look like said demon monster thingy, deleting all the other goofy pictures.
We then replaced the SD card. Friend goes out to check it one evening, and flicks through a bunch of random pics to see this. Cue dropping the camera and running screaming back to his house. He called the game warden and posted it on a bow hunting website, where it was stolen by some guy who took a picture of his computer screen with a camera and changed the date in paint. Said faggot then reported it to the news, claiming it happened in his home town. We tell friend that it was a prank on him, and after trying to beat us to death finds it hilarious.
Cue skeptics "debunking" it in the most retarded ways possible that made me lose all faith in their judgement. For instance, finding "proof" that the whole thing is shopped despite a real person being the base of the image, or saying that it was a CGI render of a monster from the "Resistance" games after the developers made a joke tweet of the pic, claiming that it had escaped the studios. My personal favorites were that it was a deer that had been rearranged in photoshop, or obviously fake due to the date being changed in the low res version given to the media.
Since then, we've faked a few more major monster sightings and other paranormal shit for fun that've driven /x/, cryptozoologists, and tabloids wild. Got a big one coming up that should hit the major news media in the next few months, and really make people believe in it.