Last week, the original Broadway cast recording of "The Book of Mormon" converted a lot of fans into followers.

The cast album flies onto the Billboard 200 at No. 31 with 13,000 copies sold in its first week according to Nielsen SoundScan. It marks the highest-charting cast album since "Disney's the Little Mermaid" arrived at No. 26 on the March 15, 2008, chart (20,000). The start for "Mormon" is also the best debut sales week for a cast set since "Mermaid."

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Naturally, "Mormon" also starts at No. 1 on the Top Cast Albums chart -- the 24th topper since the list began in 2006. Plus, "Mormon" notches the best sales week for a digital-only cast album, as its physical edition won't street until June 7.

The show -- with music and lyrics by "South Park" creators Trey Parker and Matt Stone and "Avenue Q" co-writer Robert Lopez -- recently earned 14 Tony Award nominations, the most of any production this year. It opened on March 24 at the Eugene O'Neill Theatre.

Lopez tells Billboard: "I can't believe how well the album seems to be selling. I was like, 'Could that be right?' But then I couldn't believe how well the show was selling either -- or how many Tony nominations we got. So I'll try to shut up, be grateful and enjoy the ride."

Ads touting the cast album have been running during airings of "South Park" on Cartoon Network, while Parker and Stone have chatted up the show on everything from NBC's "Today" to "The Daily Show With Jon Stewart." The album also received prominent placement in the iTunes Store in its debut week.