For Broadway shows, it’s starting to look like Twitter is the new black.

“Next to Normal” is posting 140-character missives from its characters; “Billy Elliot” is accepting questions to be posed to the show’s creatives, incorporated into online video segs; “Rock of Ages” is using feeds to dispense ’80s fun facts.

Heck, “Shrek the Musical” has even launched its own green-tinted social network site, Shrekster.

With social networks such as Facebook and MySpace seemingly well past the pop-culture tipping point, Broadway producers and marketers — like anyone else with a product to advertise — are getting in on the game.

“We’re in the middle of a monster transition in how shows are marketed,” says Damian Bazadona, prexy of tech-savvy marketing org Situation Interactive, which works on both “Normal” and “Billy,” among other shows.

It’s not enough these days for a legit production to have a website. It also needs profiles on multiple social networks — from mainstream Facebook to special-interest sites like Latino-based MiGente.com (for “In the Heights”) — and a constant stream of updates on Twitter.

“We try to make a distinct voice for a show through the social networks,” says Jim Glaub, creative director of marketer Art Meets Commerce, which works on “Rock of Ages.”

Sending out updates to a production’s fans on sites such as Facebook, marketers say, reps a good way to reach not just those fans, but everyone they’ve friended.

“It’s the way that we’re connecting to third-party people we wouldn’t be able to reach,” says Sara Fitzpatrick, director of interactive at SpotCo, the Broadway ad agency that developed the interactive components for “Shrek” and “Heights.”

“Billy” funnels consumer feedback from multiple online platforms to the site WeAreBillyElliot.com, where behind-the-scenes interviews (similarly distributed across several platforms) are aggregated.

As the profile of Twitter grows, so does its prominence in ad campaigns. Glaub, for instance, says they’re experimenting with ads that drive people to Twitter rather than to a show’s web domain.

“Normal,” with the help of book writer Brian Yorkey, is posting tweets that will follow the plotline of the tuner over five weeks (while refraining from spoiling the big reveal that comes about halfway through the first act).

The tweet-narrative has exploded in popularity, surpassing 70,000 followers. (That’s a big number; “Rock of Ages,” for instance, has around 2,600.)

One big selling point for social networks? They’re free, at least for as long as that tenuous economic model holds. But although it costs nothing to post something on Facebook or Twitter, the manpower needed to sustain an interactive campaign is on the rise.

“It takes a lot of people and a lot of time to hit as many eyes as we used to,” Fitzpatrick says.