Robert Pattinson confessed he once gatecrashed the "Harry Potter and the Order of the Phoenix" premiere after a day of drinking beer and eating pizza.

The "Twilight" star was staying with a friend in Los Angeles when he read online about the premiere.

Despite his "Harry Potter and the Goblet of Fire" character Cedric Diggory only featuring as a swift flashback, Pattinson decided to go and check it out.

"I'm just walking down Hollywood and it was a long walk I can't even remember, like a 45-minute walk and it was boiling hot... I'd literally been just eating pizzas and drinking beers for the whole summer and looked disgusting," Pattinson told the HFPA In Conversation podcast.

After the cast saw him in the crowd, they asked whether he'd like to join them on the red carpet.

"My agent still sends [the red carpet photos] to this day ... I was just pouring with sweat, you can just see the photos I look horrendous."

Visit Insider's homepage for more stories.

Robert Pattinson revealed he once gatecrashed a Harry Potter premiere "looking disgusting," after eating pizza and drinking beer all day.

The "Twilight" star was staying at a friend's house in Los Angeles when he read online that "Harry Potter and the Order of the Phoenix" was premiering at the Graumans Chinese Theater that day.

Pattinson, who rose to fame playing Cedric Diggory in the previous film, "Harry Potter and the Goblet of Fire," only featured as a flashback in "Order of the Phoenix," but decided to email his agent and ask whether he could still check it out.

Robert Pattinson as Cedric Diggory in the 2005 film, "Harry Potter and the Goblet of Fire." Warner Bros. Entertainment Inc.

"I'm just walking down Hollywood and it was a long walk I can't even remember, like a 45-minute walk, and it was boiling hot.

"I'd literally been just eating pizzas and drinking beers for the whole summer and looked disgusting."

The 32-year-old told the HFPA In Conversation podcast, he thought his casual stroll to the premiere would be a relatively low-key affair, until he reached Grauman's Chinese Theater and saw the swathes of Harry Potter fans.

"I got to the crowd and there's thousands and thousands of Harry Potter fans, I don't even know why I didn't think about it, I just thought it's cool I'll just walk there."

After pushing through the crowd, the main cast saw their former co-star appear out of nowhere uninvited.

"They were all kind of surprised I was there and were just like do you want to go to the red carpet and I was like err what."

Pattinson was asked by the Harry Potter cast to join them on the red carpet. Jon Kopaloff/Filmmagic

Laughing through the interview, Pattinson said his agent saw the photos online the next day and was shocked to see the star not only walking the red carpet but looking "like an unbelievable mess."

"They were like, 'What are you doing? Why are you being photographed like this? You look like you're out of your mind!'"

And as pictures last a lifetime, the actor said he'll never live down his sweaty film premiere gatecrash.

"My agent still sends them to this day ... I was just pouring with sweat, you can just see the photos I look horrendous."

Read more:

Robert Pattinson is bewildered by the popularity of 'Twilight': 'It was a strange story'

Every single Robert Pattinson movie, ranked

Helena Bonham Carter says Daniel Radcliffe used to hold all her beverages on the 'Harry Potter' set: 'He's got nice manners'