Over the weekend, Fifty Shades of Grey author E.L. James took to Twitter to make one of the most hotly anticipated (and hotly debated) casting announcements in recent history: Charlie Hunnam and Dakota Johnson will star, respectively, as Christian Grey and Anastasia Steele in the upcoming Fifty Shades of Grey film adaptation, which is due to hit theaters next year.

Though the news has been met with predictable bouts of fan outrage — a quixotic Change.org petition to replace Hunnam and Johnson with Matt Bomer and Alexis Bledel has already earned more than 20,000 signatures — the outpouring of reactions does speak to the difficulty of casting the two major roles.

Fifty Shades of Grey is an enormously successful property, but it also carries enormous risks: Any faithful adaptation of the mommy-porn hit is destined for an NC-17 rating, requiring actors who not only fit the roles described in James' novel, but are willing to bare all on the big screen.

It's been a long and complicated casting process, and many of the actors who publicly distanced themselves from the production — including Michael Fassbender, Armie Hammer, Mila Kunis, and Emma Watson — were never in formal contention for the starring roles anyway. But there are more than a few famous faces who at one point or another were seriously considered to star as the leads in the Fifty Shades of Grey movie:

1. Robert Pattinson

(Juan Naharro Gimenez/Getty Images)

Fifty Shades of Grey began life as a piece of Twilight fan fiction, so it's no surprise that Twilight stars Robert Pattinson and Kristen Stewart were some of the first names rumored to star. But while E.L. James said she thought casting the Twilight stars would be "weird" in 2012, author Bret Easton Ellis recently tweeted that James told him Pattinson was her first choice to play Christian Grey as recently as this summer. (Ellis also dismissed rumors about casting Matt Bomer or Ian Somerhalder, the two actors who have been widely reported as fan favorites for the part.)

E! Online adds that producers eliminated Pattinson early on in the casting process because they "didn't want to pay his high salary."

2. Ryan Gosling

(Frazer Harrison/Getty Images)

Hey, girl — did you want to see Ryan Gosling as Christian Grey in the steamy adaptation? Too bad. Though The Hollywood Reporter says that Gosling was "the original prototype" for the broody billionaire at the heart of Fifty Shades of Grey, he was never seriously interested in the role.

3. Garrett Hedlund

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Fifty Shades of Grey got a lot closer to landing Tron: Legacy star Garrett Hedlund, who was said to be tentatively interested in playing Christian. But despite a lengthy courting process from Universal, the actor formally passed in July.

Several reasons were cited: The Hollywood Reporter says that Hedlund "couldn't connect with the character," and a source at Us Weekly says that after Hedlund decided that "doing a possible trilogy was too big a commitment, producers wouldn't let him sign on for just one film."

4. Christian Cooke

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Producers reportedly had doubts about whether or not Charlie Hunnam — who is best known for FX's Sons of Anarchy and this summer's underperforming Pacific Rim — was famous enough to carry the film. But he reportedly won out over another relatively unknown actor who was in the running: Christian Cooke, whose highest-profile roles have come in British TV series like Trinity, Echo Beach, and The Chase.

But don't feel too bad for Cooke; his Hollywood star is likely to rise next month with the release of Carlo Carlei's Romeo and Juliet, in which Cooke plays Mercutio.

5. Felicity Jones

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Fifty Shades fans may have favored Gilmore Girls star Alexis Bledel for the role of protagonist Anastasia Steele, but it was never confirmed that the actress was in serious contention for the role. Instead, early reports favored Like Crazy star Felicity Jones, who is set to make her A-list debut with a supporting turn in next summer's The Amazing Spider-Man 2. The Hollywood Reporter says that producers thought Jones "had the look and ability" to play Anastasia Steele, but worried that she was too old, at 30, to play a 21-year-old college student.

But in the end, it sounds like Jones removed herself from the running. According to The Wrap, she's one of several unnamed young actress who turned down the role "due to the full frontal nudity it requires."

6. Shailene Woodley

(Frazer Harrison/Getty Images)

Perhaps the highest-profile actress to be seriously attached to Fifty Shades of Grey is Shailene Woodley, who earned a Golden Globe nomination in 2011 for her breakout performance opposite George Clooney in The Descendants. According to The Hollywood Reporter, Woodley was E.L. James' "early favorite" to play Anastasia, and she didn't object to the nudity that would be required for the role.

But she was ultimately a victim of her own success: Press obligations for the upcoming Divergent conflicted with Fifty Shades of Grey's planned shooting schedule, eliminating her from contention.