lonelygirl15 is epic.
LG15 is not a vlog. It's not a show. It's a community art project. Originally it started out as an ARG, but only to make it popular enough to work and give it a cool lack of a forth wall. Initially, it followed a pretty linear story, which was just the characters 'vlogging' as little hints and riddles in the background pointed to something sinister. They started a romance subplot (that was originally unintended, because they thought more people would watch if Bree was single) because people in the comments said they thought there was sexual tension between Bree and Daniel.
After a certain point, they revealed it was a game, and encouraged other people to play along. Most people just did video responses to Bree as if she was a real person, other people played characters who were freaking out and thinking it was real. The first big spin off was Cassie is Watching, a "game jacker" that pretended to be part of the canon, and set up riddles and stuff around a casually mentioned throw away character from the back story, who was probably mentioned just to cause intrigue and give people a spring board to do their own spin offs.
The main plot seemed to only go as far as Bree being involved in some kind of sacrificial ceremony. It gradually revealed that her parents belonged to some cult, and she was adopted and raised to be the person to be sacrificed in the ritual. The cult is implied to be some super big underground world-controlling organization, and the central person to their plot (Bree) isn't aware of it.
Then, one guy, whose direction and editing skills surpassed those of the creators of the series, made his own spin-off about OpAphid and Tachyon. OpAphid is supposed to be the 'field agent' side of the cult Bree's family belongs to. Tachyon is, apparently, a girl from a situation similar to Bree's, who is also on the run from OpAphid. OpAphid's videos are composed mostly of creepy text and words and symbols, while Tachyon's videos feature scenery shots (never showing her, as she's behind the camera) and hidden camera shots, and are all crazily edited with catchy music. It's implied that Tachyon's family (except for her brother) were killed by OpAphid, and she's still on the run from them, and has managed to out smart them and evade them for quite some time.
So, here's the cool part.
The creators liked the Tachyon and OpAphid videos so much they made them canon. Not only did they make them canon, they went back and said things that implied the Cassie spin off (and the spin off of the Cassie spin off, called Frank) were canon. Somehow, they pooled resources with the creators of this series, and helped them make new videos, by providing unique footage of the actors and props and stuff.
Recently, the organization that has been after Bree all along has been 'revealed' to be the fan-made OpAphid character. In a recent story arc, Daniel gets kidnapped by OpAphid, and releases a video on his own account where he's all creepy and brain washed, like he'd been heavily drugged. Bree, and the person they've been living with, Jonas (a non-fan-created character who is supposed to be a fan of Bree's vlogs and wanted to help Bree out... try to keep up) see Daniel's video. Bree wants to give in, and trade herself for Daniel. Jonas wants to try to "storm the castle" and rescue them. So, here's what happens:
In the last second, before Bree's taken away (and likely killed) by OpAphid, the editing style does a 360 to the fan-created Tachyon's style, and it's implied that Tachyo and her brother come in and save Bree, Daniel and Jonas.
So, basically, the plot of a series (which is making millions of dollars by the way) has completely shifted into the direction of a side-plot made by a more competent fan. Which is really really cool.