Matt Stone, one half the “South Park” writing duo, is not now, nor has he ever been, a Mormon. Neither is his creative partner, Trey Parker. They don’t have Mormons in their family trees, despite rumors to the contrary circulating madly online and in Mormon circles.

“If we did have that,” Stone said in a recent phone interview, “we would never hide it.”

What they do have is affection for and fascination with Mormons, said Stone, explaining why the pair joined Broadway musician Robert Lopez to write and direct a musical, “The Book of Mormon,” opening today (March 24) on Broadway.

In a wide-ranging exchange, Stone reflected on why they chose to write the play about Mormonism, the story they hope to tell and its universal themes.

Here are Stone’s responses, edited for length and clarity:

Q: How did you become interested in Mormonism?

A: We both knew Mormons growing up in the Denver area. It’s not Salt Lake City, but there’s a lot of seepage into Colorado of Mormon people and culture. We found the whole story fascinating. There’s just not another thing like that in America, where a whole state or region was settled by this group of people with their own religion.

The creation myths of Mormonism and what the Book of Mormon purports is so outlandishly silly to outsiders, yet all three of us have had tons of Mormon friends ... and to a person, they’ve always been nice. I need to square that with the goofy stories. That doesn’t mean we’re not going to make fun of a lot of the stuff in it, but it really comes from a loving place.

Q: What did you think about Joseph Smith?

A: He had impact, whether he was a genius con man or was inspired or talked to by God. The stories of a religion like Christianity are all based in the Old World, Jerusalem. [Smith’s] idea is taking America and Americans and putting them as central characters in this cosmic narrative ... There’s something really powerful about that.

We are storytellers. When you come up with something that just makes sense, sometimes you wonder, where does that come from? It does seem kind of inspired.

We’d like to feel even though we are atheists from outside the faith, these stories have even touched us and now we are going to do our own version.

Q: How did you research Mormonism?

A: I’ve read several dusty old books. Now we just go online really quick. Trey and I have been to Temple Square a half-dozen times over the years and taken the tour.

We spent time hanging out in downtown Salt Lake, eating at random restaurants. We’d always ask the waiters, who were usually about 25, post-college kind of people: “Do you know any missionaries?” Every single one was like, “Yes, me. Or that guy right there.” Then we’d ask if they knew anyone who was gay in the church and they’d say, “Yes, me.”

A couple of summers ago, we went to the Palmyra pageant. We went to where the Book of Mormon was printed.

Q: Do you think people might stay away because it’s too Mormon in its approach?

A: Maybe. But people who know nothing about Mormons will walk out learning something for real, like, this is kind of what their major tenets are. A lot of people know just enough to feel smug. “Oh, I got that joke. I know how it is, like how God changed his mind about blacks in 1978.” Hopefully, there’s just enough [universal appeal.] Two Mormon missionaries who get paired together has to work on its own and has got to move you outside of any religious theme.

Q: One Mormon viewer said some anti-Mormons wouldn’t like it because it isn’t mean enough.

A: That’s a criticism we can take because we never wanted to be mean. You don’t go to the theater to watch something mean. That’s no fun.

Q: Mormon viewers also said you couldn’t get to the sweet ending without the irreverence. Today’s audiences wouldn’t accept it.

A: Sending two kids to Africa, what are you going to do? It’s Africa, sub-Saharan Africa in a war zone. Bad (stuff) happens. It’s a really tough place to live and something they’ve never experienced.

We wanted to end the musical with people looking to the sky and saying, “Thank you, God.” A great place to start if you want to tell that story is “(Expletive) you, God.” That’s the story. The whole point is that one man’s blasphemy is another man’s religion. 

Peggy Fletcher Stack writes for “The Salt Lake Tribune.”