British sci-fi TV series Doctor Who has had a long and storied history since its first airing in 1963 (and its 2005 revival). Although its iconic protagonist, the Time Lord known only as “the Doctor,” never seems to truly age, he’s gone through quite a few changes in appearance and demeanor over his past 11 regenerations. Matt Smith, the Eleventh and current Doctor, has announced his intention to pass on the sonic screwdriver after this year’s 50th anniversary and Christmas specials, leaving the field wide open for speculation as to who will commandeer the TARDIS next. Each previous Doctor has brought his own flair to the role, but while it’s hard to imagine anyone else in Tom Baker’s striped scarf or David Tennant’s classic Converses, casting decisions could have gone very differently. 

1. Hugh David

The first would-be Doctor, Hugh David, was also the first actor to be turned down for the role. David had the distinct honor of receiving an offer to originate the Doctor’s role by Rex Tucker, a personal friend who happened to be a member of the production team preparing for the series’ launch. When the show finally named Verity Lambert as its producer, however, she made the executive call that David, aged 38, was too youthful to play the wise and relatively wizened Doctor she envisioned. He was passed over in favor of William Hartnell, an actor two decades his senior, though the smooth-faced Matt Smith would later be cast as the Doctor’s eleventh incarnation at the tender age of 28. David instead went on to direct an episode each of the show’s fourth and fifth seasons, leaving his mark on the Whoniverse that way.

2. Geoffrey Bayldon

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Theater-trained thespian Geoffrey Bayldon was lined up as a potential First Doctor after Verity Lambert said no to Hugh David’s youthful visage, but he wasn’t thrilled by the lengthy commitment the role would have required of him. He was also concerned about being pigeonholed into “old” roles. Instead, he took on another starring role on British television: Catweazle, a befuddled wizard from the 11th century (above) accidentally thrust into the 1960s, in stark contrast to the more experienced time-traveling Doctor. After Catweazle took off, Bayldon was devoted to the career-defining role and refused a second offer to become the Second Doctor.

Bayldon appeared in a supporting role as Organon in the show’s seventeenth season, but by the new millennium, he finally consented to take on the mantle of the Doctor—albeit only as a voice actor in the alternate-universe Doctor Who Unbound audio plays. He was 80 years old when the second of his two episodes aired, making him the oldest actor to ever play the Doctor and rendering his earlier objections highly ironic.

3. Richard Griffiths

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Venerated stage and screen actor Richard Griffiths, renowned in England as Uncle Monty of Withnail & I and the original Hector of Alan Bennett’s The History Boys but more generally recognized as Harry Potter’s nasty Uncle Vernon, was twice considered a possible Doctor. He was on the shortlist to succeed Tom Baker, but was passed over in favor of Peter Davison. Producers kept him in mind, and again considered casting him as a replacement for Sylvester McCoy, but the show was cancelled before Griffiths could set foot in the TARDIS.

4. Catherine Zeta-Jones

Recently, some Whovians have campaigned to have a woman cast as the Twelfth Doctor (and other fans’ resulting pushback). But the notion of a “Time Lady” isn’t new to the 21st century. Russell T. Davies, the writer/producer responsible for the series’ 2005 revival, was intrigued by the prospect of a female Doctor. The Welsh native put forward the name of fellow country(wo)man Catherine Zeta-Jones as David Tennant’s potential successor—certainly a more glamorous choice than had ever been considered, but one with a long history of diverse dramatic roles to her name. However, Davies had no real pull with the casting decision, as he turned the show over to Steven Moffat in 2010, who in turn ushered in the reign of Matt Smith’s bow ties.

The idea of a female Doctor was also floated in the '80s, when the series was experiencing a ratings slump so severe that it was put on temporary hiatus from airing. Sydney Newman, the show’s original creator, suggested reviving audiences' interest with a female lead. He was called in to advise BBC One on how to bolster the show’s reputation. His plan consisted of temporarily bringing back Patrick Troughton as the Second Doctor before regenerating the Seventh Doctor in female form, though not “a flashy, Hollywood Wonder Woman because this kind of heroine with no flaws is a bore.” Candidates for this game-changing new Doctor included Frances de la Tour, Joanna Lumley, and Dawn French—all well-respected, established actresses felt to be equal to the historic role. The BBC nixed Newman’s radical proposal, choosing to keep the Time Lord a lord, not a lady, and the show’s waning popularity led to its 1989 cancellation.

5. Liam Cunningham

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The crowded field of aspiring Doctors vying for the part after Sylvester McCoy stepped down attests to the show executives’ confusion about who could best rekindle Doctor Who’s former glory. Irish actor Liam Cunningham put in a bid to become the Eighth Doctor, using both his natural Dublin accent as well as a put-upon “neutral American” one. Though neither voice netted him the job, he appeared as Captain Zhukov in the revived series. He now features on TV screens as Davos Seaworth in Game of Thrones.

6. Billy Connolly

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Better known as a comedian and folk singer, Billy Connolly was another contender for the Doctor’s eighth regeneration. Though he was shortlisted for the part, it seems the decision was never his to make, as he says the opportunity “came up in a meeting, apparently, but nobody told [him] until after they had decided against it.” He claims he would have accepted the role with plans to play “a much angrier Doctor Who,” but unfortunately for Connolly, no one told his higher-ups that. 

7. Mark McGann

Liverpudlian Mark McGann auditioned for the role of the Eighth Doctor at the same time as his older brother Paul. In a double blow to Mark, he didn't get the part—but his brother did. Talk about sibling envy.

8. Hugh Grant

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Romantic comedy lead Hugh Grant now seems an unlikely choice for a sci-fi hero, but he was one of the first actors approached when casting a Ninth Doctor for the 2005 series revival. Grant turned the part down due to skepticism about the show’s potential to succeed, but he later got a second chance of sorts when playing one of the Doctor’s regenerations in a 1999 spoof production for charity (which also featured fellow would-be Doctor Joanna Lumley). With trademark self-deprecation, the actor notes that while he regrets his choice, it might have done the show some good, as he’d “probably make a mess of it” anyway. 

9. Bill Nighy

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Bill Nighy also said no to playing the Doctor, but unlike fellow Love, Actually castmate Grant, his refusal was due to a premonition that the show would take off and garner him an excess of unwanted media scrutiny. It was a character, he claimed, that came with “too much baggage.” He did, however, make an uncredited but significant appearance in 2010 as Musée d’Orsay curator and Vincent van Gogh enthusiast Dr. Black.

Although Nighy only recently disclosed his historic offer, he didn’t necessarily indicate at what point he turned down the opportunity. Out of respect to “whoever did” take the role, he has refused to say which Doctor he might have been. Despite speculation that he might have been the Ninth Doctor, Nighy’s career has spanned most of the show’s 50-year run, so there’s really no telling.

10. Eddie Izzard

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Cross-dressing comedian Eddie Izzard was once rumored to have been cast as the Tenth Doctor, with word coming straight from the mouth of the Fourth Doctor himself. Former Doctor Who star Tom Baker claimed on BBC Radio Five Live in 2003 that Izzard had landed the role, touting Izzard as “mysterious and strange and seem[ing] like he has a lot of secrets”—all qualities befitting the inscrutable Doctor. The BBC itself discounted his comments as mere "speculation," and a spokesman said simply that no decision had yet been made.

11. Michael Jackson

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The King of Pop could have been the man from Gallifrey. In the late 1980s, at the height of Jackson’s on-screen success with Moonwalker, Paramount Pictures proposed a full-length Doctor Who film starring the chart-topping singer. It’s not clear that he was offered the role of the Doctor himself, though the information lends itself to that interpretation, but the role was substantial enough that execs had a second choice in mind should Jackson turn it down: Bill Cosby.