At around 6 p.m., people began lining up. By 6:30, a line of hundreds of people wrapped around the walls of the San Diego Convention Center. A half hour before the 7:15 event started, the security guards had to stop people from joining the line.

The organizers of Comic-Con underestimated the draw of RiffTrax Live. It’s a simple concept: Three men (Mike Nelson, Kevin Murphy and Bill Corbett) watch movies. Good movies, bad movies, old movies, new movies - they don’t discriminate. As far as they’re concerned, every genre is ripe for satire.

Through an excruciating process - during which Nelson said they watch each movie at least 30 times - they come up with jokes, puns and other carefully constructed quips that mock what’s going on onscreen. They upload the track as an mp3 to their Web site, and a RiffTrax is born.

If the three names sound familiar, it’s because they were the hosts of “Mystery Science Theater 3000,” a TV series that premiered in the late ’80s. The premise: A low-level employee is shot into space by the company overlords and is forced to watch bad movies as part of an evil experiment. The show went off the air in the early 2000s, but in this most recent incarnation, Nelson, Corbett and Murphy create mp3 commentaries that fans can purchase and play over the DVDs they already own. The trio also gets back to its roots by offering video shorts and old safety videos with its trademark brand of humor.

In the amount of time they’ve been doing this, they’ve amassed a large following - many of whom showed up to their event, and many of whom were turned away. For the lucky 1,200 or so who got in, they got to watch Nelson, Murphy and Corbett riff on a 1970s Caterpillar construction vehicle safety video called “Shake Hands with Danger.”

One of the fans who made it that night was Autumn Elliott, who drove to San Diego from Arizona. Elliott said she has been a fan of Nelson, Murphy and Corbett since their “Mystery Science Theater 3000” days.

“RiffTrax is a new way to view movies you already know and love,” Elliott said. “I always think of it as being in a theater with people who are talking, but you want to hear them.”

The RiffTrax team delivered punch lines sharply, quipping, “He’s not shaking hands with danger, he’s giving it a hot oil massage” and (after a construction worker tripped over the edge of a crane), “Man, I really fell on my keys.”

Nelson, Murphy and Corbett also let fans give suggestions for the next movie for the group to work their magic on. Ideas ranged from “The Shawshank Redemption” (“I think you guys could make it funnier than it already is,” the recommender offered), “Dreamcatcher,” “Highlander II,” and “Watchmen” (“But what about the blue dangly?” Nelson said).

Another attendee suggested “Transformers 2,” because of the obvious allusion to robot genitalia.

“The word is ‘dangly,’” Nelson said.

When another fan proposed “The Rocky Horror Picture Show,” Murphy said, “That movie makes me want to die, just so you know.”

After the show, the three men talked about their careers as professional snarkers, the evolution of “Mystery Science Theater 3000” to RiffTrax and the writing process. After the original show ended, the team experimented with the idea of selling CDs to play along with the movies or videos with the commentary overlaid.

“We had DVD distribution nightmares,” Murphy said.

But once mp3s rose to popularity, Nelson said he realized that they had found a perfect medium through which to spread their observations. RiffTrax is the primary career of all three.

“We all do other writing, but no 9-5 job. We’re too lazy,” Corbett said.

The RiffTrax Live event at Comic-Con was just a preview of an upcoming milestone: On Aug. 20, the trio will be doing a live riff that will be broadcast to movie theaters nationwide. Murphy said that they’re excited to let such a large audience experience a live riff with them.

“If we were doing this on the road, we could only visit major cities,” Murphy said. “But now it can go to small towns, to people who would never have been able to see a live RiffTrax.”