SAN FRANCISCO — Some of the actors on NBC's drama "Heroes" are among those in Hollywood who might have the superpowers to help Twitter break into prime-time.

Greg Grunberg, who plays a Los Angeles cop with the ability to hear people's thoughts, pulls out his iPhone nearly everywhere, including between takes on the studio lot, to tap out the short Twitter messages known as tweets. He broadcasts them to the more than 20,000 friends and fans following him.

A tweet Grunberg sent recently about season three winding down — "Tough to say goodbye to crew not knowing if any or all of us will return next year" — sent a chill through the show's fandom. Within three minutes, their worried messages prompted him to clarify that the show "IS coming back" for a fourth season, "but some crew take other jobs, so it's tough."

For the most part, glam — not geek — still rules show business. Twitter is on the front edge of Internet innovation that's starting to change that. It allows users to send blurbs of as many as 140 characters to everyone in their network via text messages or the Web, and to sign up to follow people who interest them.

Grunberg isn't the only Hero on Twitter. Brea Grant, who plays his romantic interest Daphne Millbrook, is there. So are James Kyson Lee, who plays Ando; David H. Lawrence, who played villain Eric Doyle; and even the show's makeup artist and prop master.

"It's an official time-passer on the set," Grant said.

The ranks of Twitter-using show-business people are swelling: married actors Ashton Kutcher and Demi Moore, "The Office" star Rainn Wilson, "The Closer" creator James Duff, Emmy-winning TV director Greg Yaitanes, who invested in the company, and talk-show host Jimmy Fallon, among many others.

Twitter hasn't quite hit the mainstream yet, but it's one of the fastest-growing online services. Thirtysomething Internet entrepreneurs Evan Williams, Biz Stone and Jack Dorsey run Twitter, which started as a side project inside a podcasting company called Odeo Corp. Twitter became a separate company in 2007, and its 30 or so employees now work out of a San Francisco loft.

Twitter faces growing questions about how it will make money, since it doesn't run advertising or charge for accounts. Its regular outages have become a running joke among its users.

Still, Twitter's star is definitely on the rise. The company's founders turned down a $500 million buyout offer from social networking giant Facebook Inc. in November and closed a $35 million round of venture capital funding in February.

The service attracted 2.6 million U.S. Web users in January, a sharp increase from 178,000 a year earlier, according to research company ComScore Inc. And that doesn't include the many more people accessing the service through mobile devices or the Twitter application that runs on Facebook and other Web sites.

Laura Roeder, a Los Angeles consultant who persuaded Grant to try Twitter, says too many actors allow fan sites or celebrity media to define them. She recommends that they use Twitter and other online tools to take ownership of their online identities and talk directly to their fans.

"The more exploitative the celebrity press gets, the more Hollywood will realize this is needed," Roeder said.

Grant, who sends tweets several times a day to her nearly 13,000 followers, says Twitter has helped build her brand and reputation. "I think it's good for people to see that we are real people who have real emotions and do real things," she said.