It attracted millions of viewers, even after the staging was announced.
The film makers called a press conference after a year, following increasing suspicion among fans and the media that the central character, Bree, was not a real person.
Co-creator Mesh Flinders, speaking before the new video was uploaded, told the Guardian that he did not think the project would work in today’s climate.
“On YouTube now we wouldn’t get away with this for 30 seconds,” he said.
“People would know she’s fake immediately.”
The show, which ran for two years, grew a cast of characters and frequently referenced a mysterious and sinister religion. The storyline became a fight against an organisation called The Order.
It continued to run after Bree was killed off – but she is back in the new video, which includes some hidden material.
“I know, you’ve got a lot of questions. Questions deserve answers. It’s the only thing that satisfies them and I have many…” reads the accompanying text.
Those leaving comments beneath the video seem as amazed to discover that they have been on YouTube for 10 years as they are about the new material.
There is a mixture of surprise, delight and confusion in their reactions to the video itself, as well as some saying they think the series has had its day and should not be resurrected, while others question whether the new video is a hoax.
Actress Jessica Lee Rose, who played Bree, said that when she first discovered the role was for an internet show and not a movie, she almost pulled out.
“I instantly thought this is some scam. I really thought this was what I’d been warned about moving to Los Angeles,” she said.