The Broadway production of “Natasha, Pierre and the Great Comet of 1812” may be much larger than the original version at Off Broadway’s tiny Ars Nova, which had an audience of less than 90 people each night. But it’s still an up close and personal affair — especially for the folks seated onstage.

At the show’s Nov. 14 opening, Michael Emerson (“Person of Interest,” “Lost”), sitting a table next to his wife Carrie Preston (“True Blood”), was quickly enlisted for a brief cameo. Denee Benton (“Unreal”), who plays lead Natasha opposite Josh Groban as Pierre, found herself playing a scene at a table sitting beside Phillipa Soo, the Tony-nominated “Hamilton” actress who originated the role of Natasha. Jesse Tyler Ferguson, Richard Kind and Robin Lord Taylor also found themselves seated in the middle of the action.

“It’s so different from doing concerts, where you can kind of gaze out and sing to the abyss,” said Groban at the “Great Comet” afterparty at the Plaza Hotel. “It’s a little unnerving when you turn to sing into someone’s face and you’re like, ‘Oh, that’s Phillipa Soo. Hi. Sorry to spit on you.’ ”

To hear the cast tell it, Broadway audiences are a lot better behaved than the ones who came to the show at Ars Nova — and especially at Kazino, the downtown drinks-and-dinner venue where the show had a commercial run a couple of years ago.

“At Ars Nova we had free vodka on every table, so the audiences got a little rowdier,” recalled Dave Malloy, the show’s creator. “But I also think they wept a little more.”

Kazino, meanwhile, was like boot camp, according to Lucas Steele, the actor who’s been with the show since the beginning.

“Everything you could imagine that could happen — or couldn’t imagine! — happened,” he said. “I snatched phones out of peoples’ hands when they were taking pictures of their friends while I was doing a scene. We saw people vomit in their purse. We had a house manager carry someone out of the tent because they were so intoxicated. This list is long.”

On Broadway, the musical has proven an unexpected box office powerhouse — likely fueled by the enthusiastic fanbase of Groban. As Pierre, the singer-actor is nearly unrecognizable in a schlubby fat suit and a bushy beard.

The facial hair is real; it took about a year to get it to its current state. “I’ve grown to love it, now that it’s in the soft phase and not the itchy phase,” he said. “It’s like a human mask I get to wear.”