Last week, hours after thousands of girls had lined up at Galleria Dallas in hopes of securing a spot at an autograph session with him that afternoon, Robert Pattinson shook his head and gave a little embarrassed grin.

COURTNEY PERRY/DMN

Robert Pattinson plays the handsome, brooding vampire Edward Cullen in Twilight, based on the first of a series of novels by Stephenie Meyer.

"I really didn't see it coming at all," he said of his sudden stardom. It's especially bewildering, he noted during an interview at Hotel Crescent Court Dallas, since these fans have yet to see him on the big screen as Edward Cullen, the handsome, mysterious vampire at the heart of Twilight, the first of Stephenie Meyer's best-selling series of novels.

But fans of Ms. Meyer have already checked out the hunky, soulful and slightly dangerous-looking 22-year-old British actor online, watched the Twilight trailer and, evidently, approved.

The film opens today, and already it looks to be a blockbuster. As of two weeks ago, hundreds of screenings had sold out in advance, putting Twilight's ticket sales ahead of High School Musical 3's at the comparable time.

Mr. Pattinson, best-known previously for playing the gallant, doomed Cedric Diggory in Harry Potter and the Goblet of Fire (he did a reprise in a flashback in Harry Potter and the Order of the Phoenix), had not even been sure he wanted to be Edward.

Sure, about 3,000 other actors wanted the part badly. But the idea of playing a vampire seemed, as he put it, silly.

Then he went to an audition with Kristen Stewart as Bella, the human who wins Edward's heart in this Romeo and Juliet-tinged romance. The audition lasted 31/2 hours, and he didn't want it to end.

"I had such a good connection with Kristen. It elevated the lines," he says. "So often I would go to an audition and not really want the part. I came out of this saying I had to get it."

Once cast, he was a bit intimidated by the challenge of playing a man described as perfect in the book. But as he delved deeper, he saw Edward as someone who struggles within, fighting his desire for human blood with increasingly heroic amounts of self-control.

"It's impossible for someone so lonely and hopeless to be a perfect guy," he says. Which suits him fine, because Mr. Pattinson doesn't see himself as a perfect person. Or even a star, just yet.

"It's so strange," he says, with that grin again, of the girls who started lining up at the store before 6 a.m. for a chance to meet him more than 12 hours later. "I guarantee you if any of the girls spent a dinner with me, they'd be so bored. I never do anything interesting."

It's clear, though, that this is a young man on the cusp of celebrity, even if he is the last to see it. He has one foot in his old life, where he loves to play piano and guitar and do theater.

And then, there's a foot in this new life that's about to begin. One that he glimpsed on the Harry Potter set, as he witnessed the celebrity that hit his fellow Brit, Daniel Radcliffe.

Many parallels have been drawn between Pottermania and the Twilight frenzy, including Twilight opening on the very day Harry Potter and the Half-Blood Prince vacated when it was rescheduled for a summer 2009 opening.

But the comparison that Mr. Pattinson prefers to focus on is the way Mr. Radcliffe has pursued his own dreams while still being the ultimate Harry to millions of fans. The actor's decision to star as the troubled youth in Equus in London and on Broadway particularly impresses Mr. Pattinson.

"Daniel isn't afraid to go off the rails," he says. "It's as if he's saying, 'I'm going to live my life as I want to live it.'

"I hope to do the same."See reviews and more online at GuideLive.com and in today's GuideDaily section.