Ron Weasley Tangles With Teen Years in 'Harry Potter and the Half-Blood Prince'

Rupert Grint has spent nearly half his life as Harry Potter's best friend, Ron Weasley.

"It's been an amazing few years, which started when I was 10 or 11," Grint, 20, said in an interview for ABC News Now's "Popcorn With Peter Travers."

Grint is starring in the sixth and latest Hogwarts film, "Harry Potter and the Half-Blood Prince," which opens Wednesday in theaters throughout the country

The film premiered in London last Tuesday during a torrential downpour, soaking the "Harry Potter" cast, including Grint, who had just recovered from a bout with the swine flu.

"It was just like any other flu," he said. "It started with a sore throat and I stayed in bed for a while. I had to be off for five days but it was nothing to worry about and cleared itself up quickly."

Weasley, Grint said, has changed a lot in the latest installment -- he has a girlfriend for the first time and finally joins the Quidditch team, which plays the fictional sport developed by Rowling.

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"The Half-Blood Prince" explores the adolescent struggles of Ron and best friends Harry (Danielle Radcliffe) and Hermione (Emma Watson). Harry ends up dating Ron's sister Ginny (Bonnie Wright), while Hermione pines for Ron, who has a girlfriend but really cares for Hermione.

"Harry Potter" fans have been waiting for a major kissing scene between Ron and Hermione, which completely changes their relationship.

"We filmed it, Grint admitted. "I have known her since I was nine -- we're more like brother and sister, really, so it was kind of weird. The hardest part was pulling back from the kiss and looking at each other like we're in love without laughing."

In short, Grint has had to rely, increasingly, on his acting skills.

"At first, I wasn't concerned about acting -- just reading my lines," Grint said. "But, over the years, I have become more comfortable."

Grint's experience has expanded with the various directors with whom he has worked. In the eight years since the release of the first film, "Harry Potter and the Sorcerer's Stone," the cast has been led by four different directors: Chris Columbus, Alfonso Cuaron, Mike Newell and David Yates.