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Rachel McAdams - Allie Hamilton in ‘The Notebook’ -

While she is also known for playing resident bully Regina George in ‘Mean Girls,’ Rachel McAdams’ depiction of Allie Hamilton in love story ‘The Notebook’ was pivotal in her career.

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Rachel McAdams - Allie Hamilton in ‘The Notebook’ -

The part almost went to Jessica Biel instead. How different the film could have looked!

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Daniel Craig - James Bond in ‘Casino Royale’ -

Theater-trained Daniel Craig almost lost out to 'X-Men' star Hugh Jackman for the 007 role that would go on to define his film career.

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Daniel Craig - James Bond in ‘Casino Royale’ -

Jackman was approached for the Bond part after filming the first 'X-Men' film in 2000, but he turned it down because he wanted to diversify his portfolio.

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Jennifer Aniston - Rachel Green in ‘Friends’ -

Jennifer Aniston is still most often associated with the iconic role of Rachel Green. According to producers, however, the part was originally designed with co-star Courteney Cox in mind.

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Jennifer Aniston - Rachel Green in ‘Friends’ -

Had Aniston accepted a position on 'Saturday Night Live' instead, the sitcom could have turned out very differently.

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Courteney Cox - Monica Geller in ‘Friends’ -

According to creators, the part that Courteney Cox went on to secure was, in fact, written for Janeane Garofalo.

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Courteney Cox - Monica Geller in ‘Friends’ -

But Cox was apparently so impressive during her audition that showrunners were forced to reconsider.

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Harrison Ford - Indiana Jones in ‘Raiders of the Lost Ark’ -

Although he’s arguably more well known for the part of Han Solo from 'Star Wars,' it's hard to imagine anyone other than Harrison Ford as the face of this archaeologist’s tale.

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Harrison Ford - Indiana Jones in ‘Raiders of the Lost Ark’ -

According to creators, however, the part was meant to go to Tom Selleck, who only missed out due to complications with negotiations.

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Renée Zellweger - Bridget Jones in ‘Bridget Jones’s Diary’ -

American actress Renée Zellweger almost lost out on the career-defining role to her British counterparts Kate Winslet and Helena Bonham Carter.

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Renée Zellweger - Bridget Jones in ‘Bridget Jones’s Diary’ -

If it hadn’t been for the PR efforts of co-star Hugh Grant, Zellweger could have been trumped by non-believers who felt that the role of the British 30-something should be played by someone actually British.

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Bryan Cranston - Walter White in ‘Breaking Bad’ -

It may have been his role as dad Hal in ‘Malcolm in the Middle’ that put Bryan Cranston on the map, but it was his portrayal of science teacher turned drug dealer Walter White that made Bryan Cranston a household name.

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Bryan Cranston - Walter White in ‘Breaking Bad’ -

According to creators, it took a lot of persuading to cast Cranston over other competitors like John Cusack and Matthew Broderick—they simply couldn’t picture Hal as one of television’s most formidable narcotics dealers.

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Sarah Jessica Parker - Carrie Bradshaw in ‘Sex and the City’ -

It's hard to imagine anyone other than SJP for the role of fashionista Carrie Bradshaw in this infamous sitcom, but it almost wasn't to be.

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Sarah Jessica Parker - Carrie Bradshaw in ‘Sex and the City’ -

The creators’ favorite for the part was originally Dana Delaney, who turned down the role because she wanted to move away from sex-oriented scripts.

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Robert Pattinson - Edward Cullen in the ‘Twilight’ saga -

‘Twilight’ author Stephanie Meyer was adamant that the part of sullen vampire Edward Cullen should go to 'Superman' star Henry Cavill.

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Robert Pattinson - Edward Cullen in the ‘Twilight’ saga -

But when it came to casting, Meyer had to concede that Cavill was too old to pass for a high schooler, and the part went to Pattinson instead.

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Meg Ryan - Annie Reed in ‘Sleepless in Seattle’ -

It's true that she had already found success with 'When Harry Met Sally...,' but Meg Ryan’s dalliance with Tom Hanks in this '90s classic secured her a fixed position on the rom-com scene.

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Meg Ryan - Annie Reed in ‘Sleepless in Seattle’ -

But she reportedly nearly lost out to Julia Roberts, who bowed out of the audition process.

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Maya Rudolph - Lillian in ‘Bridesmaids’ -

Also recognized by many for her work on 'Saturday Night Live,' Maya Rudolph’s portrayal of funny girl Lillian is the most well known of her film appearances.

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Maya Rudolph - Lillian in ‘Bridesmaids’ -

But fellow comedic actress Mindy Kaling has revealed that she herself just missed out on the role that would have earned her a place in one of the funniest female casts ever.

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Taylor Momsen - Jenny Humphrey in ‘Gossip Girl’ -

Now better known for fronting rock band The Pretty Reckless, Taylor Momsen also had an acting career that was defined by her time on The CW’s ‘Gossip Girl.’

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Taylor Momsen - Jenny Humphrey in ‘Gossip Girl’ -

But she nearly lost out on the role to then-budding actress Lily Collins, daughter of English musician Phil Collins.

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Jonathan Bennett - Aaron Samuels in ‘Mean Girls’ -

According to co-star Daniel Franzese, Jonathan Bennett was only second in line to play the part of Cady Heron’s crush in the hit high school comedy.

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Jonathan Bennett - Aaron Samuels in ‘Mean Girls’ -

Bennett apparently bagged the part when the first choice was fired for too-cool-for-school behavior at a casting dinner.

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Jamie Foxx - Django in ‘Django Unchained’ -

Admittedly, Jamie Foxx had long accepted his Oscar for 'Ray' by the time ‘Django Unchained’ came around, but it was still a career-defining role. Yet it nearly turned out very differently when Will Smith was almost cast as the protagonist.

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Jamie Foxx - Django in ‘Django Unchained’ -

The ‘Fresh Prince of Bel-Air’ actor turned down the role because he couldn’t get fully on board with the story.

See also: Jamie Foxx—the king of impressions.

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