TORONTO — Camels loitered by the curb, but the sheikh arrived by sedan.

There was a bottleneck on Bloor Street here, outside the flagship theater for the Hot Docs Film Festival, which for 21 years has been the largest documentary survey in North America. Ticket holders jockeyed for sidewalk space among turbaned wrestlers in fake mustaches, whirling belly dancers, and two mangy, skittish, single-hump camels. At the center of the carnival was 74-year-old Khosrow Ali Vaziri, better known by his professional stage name, the Iron Sheik, who went from Iranian immigrant to wrestling champion to drug-addicted has-been to social media sensation to the subject of the documentary “The Sheik.”

Street spectacles may not normally be associated with nonfiction films, but some of the most celebrated and profitable documentaries of recent years have become phenomena extending beyond the screen, with subjects attaining a kind of stardom and serving as major players in a film’s promotion. But even as the subjects become more central to the success of films that scrutinize their lives, they rarely have any creative input in the projects they’re promoting.

Khosrow Ali Vaziri, center, better known as The Iron Sheik, with the executive producers of “The Sheik,” Jian Magen, left, and Page Magen, answering audience questions after the film’s premiere in Toronto. CreditJoseph Michael Howarth/Hot Docs

Which isn’t to say that subjects can’t benefit from a film’s success. In the two most recent Academy Award winners for best documentary feature, “20 Feet From Stardom,” about backup singers, and “Searching for Sugar Man,” about the forgotten singer-songwriter known as Rodriguez, musicians went from obscurity to a measure of fame thanks to the success of the features.

The director Malik Bendjelloul recalled how anonymous Rodriguez was before the film’s first screening at the 2012 Sundance Film Festival. “Many people didn’t know when the film started who he was at all,” he said. “They even thought that he was dead for the first half-hour. So seeing him in the flesh an hour later was powerful. That’s what you can do with documentaries.” Within the year, Rodriguez was performing at Radio City Music Hall.

Even celebrity-free documentaries, like the Hot Docs selections “The Overnighters,” “Bronx Obama” and “Hotline,” tour the festival circuit with subjects in tow. Their presence exploits the inherent drama of in-person appearances mere seconds after their lives have been projected on the big screen. But if post-screening discussions help create buzz around documentaries, they also allow subjects to present their own version of events.

At a showing here of “The Overnighters,” about a North Dakota boomtown inundated by unemployed men, the director Jesse Moss, and Jay Reinke, the pastor who ministered to the men, talked openly about their differing desires for the film’s ending. At the Tribeca Film Festival last month, Matthew VanDyke, an American who joined the Libyan uprising, expressed mixed emotions about “Point and Shoot,” a documentary about him that relies heavily on his own first-person footage. “There were a lot of things that weren’t in the film,” he said.

Charlotte Cook, director of programming for Hot Docs,  talked of the bravery required of  noncelebrities who appear in films “because that becomes a public representation” of who they are. With that in mind, Ms. Cook has invited more subjects to the festival in recent years to speak on their own behalf and to mingle with members of the film world.

At an after-party, several filmmakers even admitted to being star-struck by Mr. Reinke. “Festivals are always under huge pressure to have celebrities, because that’s what generates press,” Ms. Cook said. “We made this really conscious decision to define our own version of celebrity, and that tends to be the subject.”

After the screening here of “The Sheik,” which charts both Mr. Vaziri’s heyday as a wrestling villain and the depths of a drug habit that derailed his career, he briefly slipped into his bombastic character (“Give me a hell yeah!” he demanded of the crowd) but otherwise sat quietly in his wheelchair and ceded the floor to the producers Jian and Page Magen, Don Kings in training who spoke freely and colorfully on his behalf. By contrast, the filmmakers played supporting roles during the post-screening discussions for “To Be Takei,” a loving portrait of the “Star Trek” actor George Takei, and “I Am Big Bird: The Caroll Spinney Story,” which profiles the beloved Muppeteer.

From left, Jane Jankovic, a producer, hosting a question-and-answer session featuring Oscar the Grouch, Caroll Spinney, Debra Spinney, and Dave LaMattina and Chad Walker, directors of “I Am Big Bird.” CreditJohn Barduhn/Hot Docs

The 80-year-old Mr. Spinney sat with his wife, Debra, whose library of home movies furnished behind-the-scenes footage, to hear how his characters Big Bird and Oscar the Grouch have helped define generations of children. “I was sitting there partly crying watching the movie, because it’s a very moving movie, and then I realize, it’s your life,” said Mr. Spinney, who brought the still-cantankerous Oscar out for a surprise appearance and lingered afterward to pose for pictures with fans.

After a prolonged standing ovation, Mr. Takei, 77, sat next to his husband and on-screen foil, Brad Altman, and received numerous tributes and testimonials from the audience for his work as an advocate for same-sex marriage and social justice. Much as in the film, the men presented a classic odd-couple dynamic, with the hammy Mr. Takei slipping into ribaldry, while the more button-down Mr. Altman fiddled with his husband’s wonky microphone and shook his head disapprovingly. “Always giving me orders,” Mr. Takei said. “You know what it’s like in our household — yes dear, yes dear.”

Though Mr. Altman exhibited excellent comic timing onstage, Mr. Takei said it was difficult for his husband to adjust to becoming a major character in the film, not to mention a source of comic relief, after decades of managing Mr. Takei’s career behind the scenes. “I don’t think, despite that Brad and I discussed it, he was quite prepared for how exposed our lives were going to be,” Mr. Takei said. But Mr. Altman said he saw the benefit of having their marriage portrayed by a film that the  co-director and editor Bill Weber called “a documentary romantic comedy.”

“This is going to be exposed to so many more people than if George would just do the college lecture circuit or talk to corporations,” Mr. Altman said. “People will be sitting in their living rooms, pushing a button or whatever for pay per view and watch this 90-minute documentary, and say: ‘Oh, he’s that guy from “Star Trek.” He’s gay, my relative is gay. Why would I want to discriminate against my relative?’ ” Mr. Takei chimed in, “Our mission is to make the film enormously successful.”

When a celebrity is the subject, there’s the prospect of film and filmmaker being obscured by the cult of personality. “I don’t need to be the star,” said Jennifer Kroot, the director of “To Be Takei.” “I’d like to have more opportunities for things, but I’m happy to have him out there presenting the film. It’s certainly the best publicity I can have.” Though she added, laughing, “He knows I made it.”

By contrast, Matthew Stoneman, the subject of Aaron Naar’s “Mateo,”wasn’t present for the film’s screening at Hot Docs. The movie paints a deeply complicated portrait of an angel-voiced musician who splits time between a hermetic, hand-to-mouth existence in Los Angeles and a freer, more indulgent one in Havana. Standing in the lobby after the screening, Mr. Naar weighed the benefits of Mr. Stoneman’s absence against his presence. “I completely understand that Matthew is the asset of this project,” Mr. Naar said. “To have him show up is the most amazing thing. But if you want some candid information about the back story or anything, I think it’s a bit easier for me to talk removed from him.”

“Mateo” could potentially jump-start Mr. Stoneman’s struggling music career, but it isn’t intended to be “a marketing vehicle,” as Mr. Naar put it. Besides, having a man holding a guitar onstage can forestall the sort of discussion that followed this particular screening, when Mr. Naar and a producer spoke of their decision to include footage of Mr. Stoneman consorting with Cuban prostitutes — footage that Mr. Naar said his subject was eager to provide.

So what does Mr. Stoneman think of the film? Mr. Naar said his subject hasn’t seen it. “He said it’s too personal.”