All the actors in the show—which has been running since mid-November—are between the ages of 8 and 12, and the hilarious spectacle feels something like a grammar school Christmas pageant. There’s even a mock nativity scene where the boy who plays the Church’s founder, L. Ron Hubbard, is "born" and then shown curled up surrounded by children who are on all fours and wearing pig and chicken noses (so to speak). During another part of the show, the kids portray Scientology members Kirstie Alley, John Travolta and Tom Cruise.

The show’s Web site promises the "The inspirational story of one teacher, author, explorer, atomic physicist, nautical engineer, choreographer and horticulturalist named L. Ron Hubbard who motivated millions—and made some as well," and—even before the show was mounted—this description wasn’t much to the liking of Mr. Carmichael, who sent the show’s producer, Aaron Lemon-Strauss, a letter on Nov. 5 that voiced his concern over the possibility that the musical would "ridicule" Scientology. He hadn’t been to rehearsals, but had seen that the musical’s Web site had links to various articles and Web sites that denounced Hubbard and the Church.

"The various clichés about Scientology making money from Scientology are not just clichés, but lies. Both you and Kyle [Jarrow, the musical’s author] have told me your work comes from research, not clichés," Mr. Carmichael wrote. "Real humor … is based on truth, not blindly accepted clichés.

"There are dozens of scholars and independent experts who have bothered to look at the religion and found it to be just what it says it is," he continued. "Scientology is a religion which millions of people around the world testify helps them to live a better life, and to know themselves spiritually. Scientologists are decent people, involved in the world around them, and using what they know to help others."

Himself a "decent" person, Mr. Carmichael—an affable looking large man with graying hair—clapped at the end of the performance, which he attended alone. But when reached by The Observer this week, he said he didn’t feel comfortable commenting on the show at this time.

The creators of the musical maintain that they feel the show lets the religion speak—or sing—for itself.

—Anna Jane Grossman