The Legend of Boggy Creek
In the early 1970s, an ad salesman borrowed a camera and $100,000 to make a fake docudrama about a yeti-type creature. That film went on to gross over $20 million at the box office. Watch the whole film on Youtube, here. It was a lot like the Blair Witch Project, in that it featured locals spinning "true" yarns about an area legend.
Also like The Blair Witch Project, the sequels immediately abandoned the charming docudrama format, and thus any hope of not completely sucking. The third film in the series, confusingly named Boggy Creek II, was released in 1985. This one was so bad that it earned a riff on an episode of MST3K. Yet, despite this, someone decided to pick up the narrative 38 years after the original.
2010's Boggy Creek: The Legend is True feels unfinished in that it frequently forgets to show characters' resolutions. A guy is fighting the Boggy Creek Legend off from its victim, the victim runs away and... we never find what happens to the guy. The local police show up to dispatch the monster and... two scenes later we never see or hear from them again. Also the Boggy Creek monster looks less like Bigfoot, and more like the Crypt Keeper a few years after his supply of formaldehyde runs out.
Still, they cranked out another one in 2011: The Legacy of Boggy Creek. Here's the trailer, which actually manages to misspell the name of the town in which all five movies take place. We can't wait for the Boggy Creek monster to fight the Cloverfield Monster, where our biggest fear will be throwing up in the theater from all the shaky camera shots.