Sure enough, the production is bawdy, sexually explicit and irreverent. Many believers especially older viewers or those easily offended would see it as a blasphemous assault on scriptures, much like the pair's animated TV series. But the satire and tone were not as hostile as many Mormons feared (though this was a preview and parts could change before the March 24 opening).
"I was expecting to be offended," said Anne Christensen, a 22-year-old LDS New Yorker, "but was pleasantly surprised by how incredibly sweet it was."
Her mother, Janet Christensen, added: "It's not G-rated, but they treated us with affection. And they did their homework."
The play is a story about faith and doubt, with actions and themes that will be familiar to most Utahns, no matter their religious tradition.
The set includes the outside frame of an LDS temple, with a spinning Angel Moroni on top. There are brief appearances by LDS Church founder Joseph Smith, his successor, Brigham Young, Book of Mormon figures Mormon and Moroni, and Jesus himself.
The main characters, though, are LDS missionaries in white shirts, ties and those ever-present name tags.
The first scene shows about a dozen missionaries happily ringing doorbells and claiming all answers "are in the book," holding up copies of The Book of Mormon.
For the next two hours, these young men sing about being tempted to sin, about turning off feelings of sexuality, guilt and fear, and about believing sometimes-ludicrous doctrines. They deal with differences and egos and doubt.
One mismatched pair, Elder Price (played by Andrew Rannells) and Elder Cunningham (played by Josh Gad), is sent to Uganda, where AIDS has decimated the population and the locals believe having sex with a virgin is the only cure but there are no virgins left. A warlord named Joseph Kony (named after the real rebel leader who slaughtered thousands of people in northern Uganda) is threatening to attack and circumcise all the women.
Price, a by-the-book leader who thought Orlando, Fla., would be a perfect place to do his two-year stint, is convinced that he can change the world by baptizing the most people. He is confident and cocky.
Cunningham, a geeky but eager misfit, just wants to be liked. He hasn't actually read the Mormon scripture but loves the stories of "Star Wars" and "Lord of the Rings" and mixes them into his preaching.
In one powerful number, "I Believe," Price belts out a string of peculiarly Mormon teachings that ancient Jews sailed to America, that God lives on a planet called Kolob, that in 1978 "God changed his mind about black people" and that the Garden of Eden was in Jackson County, Mo.
Later, Price begins to doubt those stories, which triggers a "spooky Mormon hell dream," in which he sees serial killer Jeffrey Dahmer and Genghis Khan, among other figures. Price is also haunted by two giant cups of coffee, which is prohibited by the church's health code.
That leaves Cunningham, who has a "problem" with lying, alone to convert the Ugandans and leads directly to some hilarious antics and miscommunication.
In the end, another Ugandan says that Salt Lake City is not an actual place but a metaphor.
"This counterbalance to doctrinal absolutism and scriptural literalism will go against the grain of many mainstream Mormons," said Glenn Cornett, a California Mormon who attended Thursday's preview, "but sits very comfortably with me and many of my friends in and out of the church."
The play did feature some of the same shocking statements that Parker and Stone use on "South Park," Cornett wrote in an e-mail, and "camp depictions of LDS religious figures [Jesus, Moroni, Joseph Smith, et al] would make some of the more-devout people a bit queasy."
But Cornett was "pleasantly surprised that the writers' usual middle-school-grade crudeness was virtually absent."
Cornett, who served an LDS mission in Thailand in the 1980s, found the play's scenarios "at once shockingly different and warmly similar to his own."
Attempts at cross-cultural dialogue between Mormon missionaries and locals in other countries "tend to lack coherence when one or both parties are so steadfast in their beliefs that they are impervious to reason and evidence," Cornett wrote. "Some of the most-bizarre moments in the play therefore were more exaggerations of my Thailand missionary experience than complete misrepresentations."
Parker told Vogue that if any Mormons watch the whole play, they will like it.
"It rips on them a lot," Parker told the magazine, "but, in the end, their spirit of wanting to help wins the day."
Chris Boneau, a spokesman for the producers, said Thursday that "this is not just a spoof of Mormons, and it's not cynical."
Parker and Stone have said they love Mormons "and it showed," said Graceann Bennett, a Mormon from Chicago. "It was like loving teasing. I don't think you could get to that sweetness in today's world without a serious dose of irreverence."
Bennett especially liked the fact that the characters were "real Mormons," not fringe groups such as polygamists. There was not a single mention of plural marriage, "Big Love," Mitt Romney or Proposition 8. And, though there is a glimpse of "Mormon underwear," there are no jokes about it.
"Americans think Mormons are all the same," Bennett said. "This shows diversity and that Mormons can grow and change in their faith."
Bennett wouldn't recommend the show to "black-and-white" believers, either pro- or anti-Mormon. For the former, the musical is too nuanced, she said, and for the latter, "it's not mean enough."
"If you can ignore some of the obscenities and raunchiness," she said, "you'll be delighted."
Janet Christensen thought the play might even trigger an interest in the LDS missionary system, seeing the characters' "sacrifices and dedication."
Many in Thursday's audience clearly were "South Park" fans.
Though he wasn't sure what the play was trying to say, Andy Farren, a lifelong New Yorker who is not LDS, found the Mormon characters "endearing."
Robert Bryan, who also is not LDS, went further.
"Mormons were portrayed as naive, sweet, innocent and stupid," Bryan said, adding a tongue-in-cheek comment that the show was "a religious experience."
This "Book of Mormon," he predicted, "will be a hit."
LDS Church statement
In response to media requests before the musical's preview, the LDS Church released the following: "The production may attempt to entertain audiences for an evening, but the Book of Mormon as a volume of scripture will change people's lives forever by bringing them closer to Christ."
Some lines from the play
• "What happened to you?" Elder Cunningham asks Elder Price, after Price's battle with doubt.
"I woke up," Elder Price answers.
"Of course you did," Elder Cunningham says. "You drank 12 cups of coffee."
• "I've never had a best friend until now," Elder Cunningham tells his missionary companion. "They all leave me, but you can't."
• "We are going to change the world together," Elder Price sings, then adds, "but mostly me."
• All the Anglo Mormon missionaries, dressed in white, sing to their recently baptized converts, also dressed in white, "They may be Africans, but we are Africa."