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OTRC: Tom Arnold talks the secret to Kristen Bell and Dax Shepard's relationship

Tom Arnold appears at the premiere of 'Hit and Run' in Los Angeles on August 14, 2012.

Tom Arnold stars in Dax Shepard's new film "Hit & Run" and the comedian / actor spoke about working with his longtime friend on the film and watching Shepard's relationship with Kristen Bell develop.

When asked at the film's premiere earlier this month why he decided to join the cast, Arnold told OnTheRedCarpet.com, "Well my buddies are in it and Dax wrote me a really good part, based a little bit on our relationship."

"We got together on a film that took about three years to shoot, no script or anything called 'Brother's Justice' and that was fun but this is like a real movie," he added. "So I definitely wanted to be a part of it and see what Dax would do and he did amazing."

In the film, Shepard plays a former getaway driver named Charlie Bronson who jeopardizes his Witness Protection Plan identity in order to help his girlfriend (Bell) get to Los Angeles. Charlie's former gang and a U.S. Marshall (Arnold) chase them on the road.

Shepard wrote the film and co-directed the movie with David Palmer. The movie also stars Kristin Chenoweth, Beau Bridges, Bradley Cooper and Michael Rosenbaum. Shepard, Cooper and Arnold worked together on Shepard's 2010 mockumentary "Brother's Justice."

Arnold explained how he knew many of the cast members prior to the shoot.

"Well Dax, I met him first like ten years ago on 'Punk'd' and he was my best man," Arnold said, referring to his fourth wedding to Ashley Groussman in 2009. "We've done a lot of stuff together. Known Bradley for about seven years and we're buddies and the other guys, I know them all. Obviously I met Kristen with Dax and she was at my wedding too. "

"They're sickeningly cute. It's disgusting," he said of Bell and Shepard.

"Here's the secret: She's amazing and he grew up and that is the secret. He's good for her too, believe me. He's good for her too, but he had to sort of earn that," Arnold added. "She was good to go sort of right [from] day one. He said if I'm going to have to be with this woman, I'm going to have to be an adult. I'm going to have to grow up. No more of that crazy stuff and that's what he did. I'm very proud of him. "

"Hit & Run" hit theaters on August 22. Check out the trailer below.

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