The cast of a film is decided by many moving factors. For that reason the actor that is the first choice for a role doesn't always end up playing it.

While the reason to drop out of something is usually schedule related, there are some actors who had to drop out of a film for reasons that are decidedly stranger.

Reese Witherspoon: Bad Scottish Accent

During an interview on ITV’s Lorraine promoting the animated film Sing, Reese Witherspoon explained that accents aren't her "thing".

 

"Scottish is really…I was supposed to do…Oh no I don’t really want to talk about it" she began when asked about the accent she finds the hardest. "I tried to do a Scottish accent once… It was bad, I had to quit the movie."

"Really? Over the accent?," her Sing co-star Matthew McConaughey laughed.

"It’s not my finest moment," Reese Witherspoon replied. "I don’t want to talk about it any more. That just came out and I really wish it hadn’t."

Though she didn't name it, the film Witherspoon had to quit was the 2012 Disney Pixar film Brave.

In an interview with Digital Spy, director Mark Andrews explained how Merida ended up being voiced by actor Kelly McDonald.

"We did have Reese Witherspoon when we started the project and she was on for quite some time, getting her Scottish accent down," he explained. "It was sounding great but as we were continuing with the movie she had other movies lining up, so unfortunately we were unable to continue with her and had to get a replacement."

Ryan Gosling: Weight Gain

Director Peter Jackson's 2009 film The Lovely Bones stared Mark Wahlberg as grieving father Jack Salmon, but that role was originally supposed to be Ryan Gosling's.

Gosling was fired from the film because the director and the producers weren't a fan of the 60 pounds he gained for the role.

“We had a different idea of how the character should look." Gosling told The Hollywood Reporter. "I really believed he should be 210 pounds,”

"We didn't talk very much during the preproduction process, which was the problem," Gosling continued. "It was a huge movie, and there's so many things to deal with, and he couldn't deal with the actors individually. I just showed up on set, and I had gotten it wrong."

Gosling was fired just days before production began.

"Then I was fat and unemployed," he said.

Luckily that didn't last long.

Anne Hathaway: Graphic Birth Scene

The role of Alison Scott in Knocked Up (2007) was originally supposed to be played by Anne Hathaway.

The Oscar winning actor ended up dropping out because she wasn't a fan of the film's very graphic birth scene and the role went to Katherine Heigl.

“My issue with it was that having not experienced motherhood myself, I didn’t know how I was gonna feel on the other side about giving birth," Hathaway told Allure. "And by the way, I could pop a kid out and think, ‘Oh, well, I really should have done that movie.'"

Hathaway is now a mother, but no word on if she regrets dropping out of the hit comedy.

Charlie Hunnam: Nervous Breakdown

Sons of Anarchy actor Charlie Hunnam made headlines when he was cast as Christian Grey in the much anticipated film adaptation of the bestselling book Fifty Shades of Grey. 

But, before filming began the Hunnam dropped out telling Moviefone he "had a nervous breakdown".

Hunnam explained that he "bit off more than he could chew" when it came to playing Christian Grey. He said he "just couldn't transition from Jax Teller [his character on Sons of Anarchy] to Christian Grey in 48 hours."

The role eventually went to Jamie Dornan who will also play Christian in the upcoming sequel.

Kristen Stewart: Age Difference

Twilight star Kristen Stewart was originally cast to play the femme fatale con woman in the 2015 con movie Focus. But when Will Smith joined the cast as her love interest, she dropped out because she felt the age difference was too large.

Smith, who is now 48, is 22 years older than now 26-year-old Stewart and has a son that is only two years younger than she is.

The role eventually went to Margot Robbie.

Robbie is the same age as Stewart.