To begin to understand Zac Efron’s particular strain of viral fame, it helps to stop by your nearest department store, drugstore, or grocery store.

A quick glance will reveal his omnipresence. He’s on gift wrap and party cups and trading cards and lunch boxes. That’s his face inside a pink, heart-shaped locket. On pajamas and night lights, cake decorations and lip balm, backpacks and umbrellas. He’s on the official High School Musical digital camera and the official HSM MP3 player. Lately he’s been leaping for joy alongside his cast mates on Honeycomb cereal boxes to plug the DVD release of High School Musical 2.

That sequel, which aired last summer on the Disney Channel, was the most-watched show in basic-cable history. The original installment—also a made-for-TV movie—set the stage for HSM mania; since its debut on January 20, 2006, it has been seen by a worldwide audience of approximately 200 million. The market-research company Soleil-Media Metrics recently estimated that the HSM franchise has contributed at least $1 billion in profits to the Disney empire.

Although there are technically six leads in High School Musical, Efron, 20, is the breakout star, and the cast member who’s become a prime target for the paparazzi. He alludes to this while we’re cruising around his L.A. neighborhood in his black Audi S6, driving past his bland, ordinary-looking apartment complex. “It annoys my neighbors that the paparazzi take all the parking spots,” he says.

Fortunately, though, they don’t seem to be following their prey to the safe haven that’s been designated for our interview: God’s house. The location Efron suggested—the Presbyterian Church of Hollywood—made me wonder initially if the biggest young star in America, whose extracurricular résumé so far remains unbesmirched by coke binges, nightclub brawls, and DUIs, wanted to talk about . . . his faith? Maybe Zac Efron had found Jesus?

Actually, no. (I find out later he was raised as an agnostic.) Efron chose this location because the church campus is being rented out by the production company for his next movie, Seventeen, for the indoor basketball court in particular; Efron’s character in the movie (like his HSM character) is a basketball whiz.

The church setting suits him. He says stuff like “Cool, dude!” with such infectious joie de vivre that I have to keep reminding myself that we’re really in Hollywood, the world’s most cynical company town. The squeaky-clean High School Musical movies were shot in Utah, and it’s almost like Efron brings a little bit of Utah with him wherever he goes (he’s actually from Arroyo Grande, California: population 16,700). He could be a lost Osmond.

On the Hollywood Presbyterian court, Efron shows off his rapid-fire between-the-legs dribble, explaining that getting the look and feel of it right took him forever: “I’ve just been doing this over and over and over again at home, practicing in my kitchen.” At five feet ten, he’s gifted with speed and agility, but his teenage growth spurt came relatively late, so for much of his childhood he was the runty, relatively unathletic kid.