Casting is everything, especially in a comedy. While the script for The Princess Bride was brilliant, it was truly the actors who brought it to life. This is even more true for the cast of a show like Seinfeld and certainly of Wedding Crashers.

The 2005 comedy was a smash-hit at the box office and with later DVD sales. The film, which was directed by David Dobkin and written by Steve Faber and Bob Fisher, made Owen Wilson a lot of money, as it did for Vince Vaughn. The two guys were the center of the comedy, which was based on the producer's real-life wedding crashing experiences and developed by the writers, director, and even the actors themselves. But the movie wasn't just about Vince and Owen's characters. A bevy of other talented actors were in charge of breathing life into this classic comedy.

Here's the truth about casting Wedding Crashers...

Involving Vince And Owen

According to an in-depth history of Wedding Crashers by Mel Magazine, the idea for the movie came up when Steve Faber and Bob Fisher were taking meetings in Hollywood. They were then tasked to write a script on the idea that eventually found it's way into the hands of Shanghai Knights director David Dobkin. While at the premiere of the movie, which starred Owen Wilson, David saw how Owen interacted with Vince Vaughn, who was also in attendance.

"We were at the after-party, and I’m talking with Vince and looking over at Owen," David explained to Mel Magazine. "I swear to God, Abbott and Costello popped into my head. I remember grabbing my agent and saying, 'I want to find something for Vince and Owen.' He knew I had been looking for an R-rated comedy. Literally, eight weeks later, he called me up and said, 'I think I just read the script.' My agent sent the script to me, and I saw what it could be for both of them — especially for Vince, because Vince and I had been looking for a movie for five years, and you don’t want to swing until you know you’ve got the thing that is going to be a bulls-eye."

After convincing Owen and Vince to do it, David then set his sights on the rest of the characters...

Filling Out Wedding Crashers' All-Star Cast

At the time, Bradley Cooper was only known for his role in Alias. He was basically unknown. Who would have thought he would be so perfect for the role.

"My saying is that you never, ever hire someone in the room — you have to always go back and watch the tape," David explained of the audition process. "Bradley Cooper is the only person who was an exception. I couldn’t find anyone [for that role], and then he came in the room and he was amazing. He was like a thoroughbred. I remember going up to him and saying, 'Dude, you’re awesome! You got the part!'"

Another virtually unknown actor who knocked it out of the park in the audition room was Isla Fisher.

"Isla Fisher was the funniest audition ever," casting director Lisa Beach stated. "She came into the room and did the scene where she puts the make on [Vaughn’s character] in the bathroom and suddenly just goes out of her mind. And Isla, dare I say, spread her legs, flopped me down on my back, and was just crawling all over me."

Related: Here’s How Sacha Baron Cohen And Isla Fisher Met

As for the character of Claire, who was eventually played by Rachel McAdams, David and Lisa had a much, much harder time finding the right actor. In fact, they claim to have seen over 200 actors for that part. It became so much that the studio (New Line Cinema) forced David to make a decision on the actor who would star opposite Owen Wilson.

"The very last person before that meeting was Rachel McAdams," David said. "She was the only person that could do the role right. [Claire] was in the middle of a somewhat misogynistic, wealthy American dynasty. I didn’t want her to hate her family; I wanted someone who felt trapped by that and you felt bad for her. You knew that she loved these people, but she was confused."

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Rachel was interested in taking the part because she immediately had a report with the director. And the actors they chose to play her parents were also enticing. Of course, we're talking about Jane Seymour and Christopher Walken.

According to Jane Seymour, every actor in her age group tried out for the part. Jane wasn't used to doing auditions anymore due to her star-power but was forced to do one for Wedding Crashers. Apparently, she killed it in the room, mostly because she thought the script was so funny and had a lot to play with.

Related: The Truth About Casting The First 'Harry Potter' Film

As for the role of Senator Cleary, the studio was interested in the likes of Harrison Ford or Burt Reynolds. But David was all about Christopher Walken because he knew that the Sleepy Hollow actor "wouldn’t have to lift a finger to make people scared of him."

Since David considered him one of the greatest actors alive, casting him was a no-brainer... He would have zero directing to do. He could just sit back and watch a masterwork.

Luckily for David, he pretty much had this experience with every actor involved... That's why great casting is so important.

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