© Digitalspy/ST - Getty ImagesPHOTOSHOP, Doctor Who, Hugh Grant, Bill Nighy, Alan Cumming
For the actors lucky enough to land the part, it's a career-defining role that guarantees you a legion of fans for life.
Even for those who miss out on the part of the Doctor in Doctor Who, it's pretty exciting just to be considered. "To be thrown into that mix as a possibility was fantastic," actor Ben Daniels told Digital Spy in 2013, having apparently been pipped to the post by Peter Capaldi.
Download the Microsoft News app for your Android or iPhone device and get news & live updates on the go.
There do exist, though, those actors who have done the unthinkable: thrown the TARDIS keys back in the BBC's face and turned down the chance to travel across all of time and space. (All right, so these days they're actually turning down a lengthy and exhausting shoot in Cardiff... but it's Doctor Who, for goodness sake!)
These are the men who wouldn't be Who.
1. Hugh Grant © Koichi Kamoshida/Getty ImagesHugh Grant in 2004
Looking for a big-name star to front his upcoming relaunch of Doctor Who in 2004, Russell T Davies enquired about Grant's availability - the Love, Actually star apparently declined, though later admitted he regretted missing out once he saw what a success the revival series became.
Many years later, Davies told Digital Spy that he suspected the offer never made it past Grant's agent, who he believes rejected it on the actor's behalf: "With that level of star, you approach the agent and they just kick it out the window. 'Would Hugh like to come to Cardiff for a year?' 'No!'"
2. Bill Nighy © Niki Nikolova/FilmMagic/BBCBill Nighy in Doctor Who
Nighy's name was also bandied about in 2004 when the search for the ninth Doctor was ongoing. He later confessed that he was up for the role at one stage, but refused to confirm if it was prior to Christopher Eccleston landing the gig.
"I won't tell you when, because the rule is that you are not allowed to say you turned that job down because it's disrespectful to whoever did it," he told the Daily Express in 2013.
"I will say that I was approached. But I didn't want to be the Doctor. No disrespect to Doctor Who or anything, I just think that it comes with too much baggage."
Nighy wasn't averse to a guest spot, though - he popped up in a cameo as an art curator in the 2010 episode 'Vincent and the Doctor', written by Love, Actually's Richard Curtis.
3. Peter Cushing © Amicus ProductionsPeter Cushing as Dr. Who
Cushing did in fact accept the role of the Doctor in the 1960s, appearing in two Doctor Who movies: Dr Who and the Daleks (1965) and Daleks - Invasion Earth: 2150 AD (1966).
The films were remakes of stories from the television series and reinvented the alien Doctor as a human scientist who travelled through time and space in "Tardis" - a self-made craft. And, yes, his name actually was "Dr Who".
But the Hammer Horror icon turned down the opportunity to play the part on television. "They did [offer it to me] at one time," he later revealed. "I couldn't [do it], because I was otherwise engaged, but even if I could, I doubt I would have done it.
"I didn't really care for the Doctor Who pictures [or] the television series... they weren't my cups of tea. And I must say, the Daleks did rather get on my nerves."
You're breaking our heart(s), Peter!
4. Alan Cumming © Chris Weeks/WireImageAlan Cumming in 2005
Having got a firm refusal from Hugh Grant('s agent), Russell T Davies apparently approached Cumming, then hot off X-Men 2, about the possibility of playing the Doctor. But there was a serious hitch - Cumming was based in New York and was unwilling to relocate to Wales.
"He said, 'It's eight months of the year in Cardiff..." And I said, 'What?' and I think that might have been what blew it. Nothing against Cardiff, but..."
Like Nighy, though, Cumming would eventually land a guest spot on Doctor Who - he appeared as the Scottish monarch King James I in Jodie Whittaker's first series.
5. Brian Blessed © Moore/Fox Photos/Hulton Archive/Getty Images/Mick Hutson/RedfernsBrian Blessed - in 1961 and today
He of the bellowing tones claims to have been considered as a potential replacement for the very first Doctor, William Hartnell, back in 1966.
"After I was in [BBC cop show] Z Cars, the head of BBC serials took me aside and said, 'We're thinking of having a young Doctor Who and we'd like to cast you', but it clashed with other things," Blessed told the Radio Times.
Blessed's loss was Patrick Troughton's gain, though Brian did insist he'd "jump" at the chance to play the Doctor these days. I mean, we're excited for Jodie, but...
6. Boris Karloff © Silver Screen Collection/Chaloner Woods/Getty ImagesBoris Karloff
Yes, actual Frankenstein's monster. Screen legend Karloff was apparently approached to play the Doctor in the late 1960s... though not on television.
A spin-off radio series was in the works, with Karloff eyed for the lead role, but he declined. Peter Cushing eventually stepped in to record a pilot, but the BBC passed on the series. The recording, tragically, is thought to be lost.
Karloff did eventually feature in Doctor Who, sort of, when footage from his 1931 film version of Frankenstein appeared in the Paul McGann-starring TV movie in 1996.
7. Geoffrey Bayldon © Tony Kyriacou/REX/ShutterstockGeoffrey Bayldon
The late Bayldon was best known for playing the title role in ITV's 1970s children's fantasy series Catweazle, playing the eccentric 11th century wizard across two series. But the actor, who also played the Crowman in Worzel Gummidge (1979-81), is believed to have turned down the part of the Doctor not once, but twice.
He was first approached at the very beginning of the series, but passed up the chance to play the first Doctor, and later declined the opportunity to replace William Hartnell.
"I've never been in love with sci-fi - it doesn't terribly interest me," Bayldon once told Sci-Fi Bulletin, insisting that Catweazle had a "magic" which the early episodes of Doctor Who lacked.
8. Peter Capaldi © BBC/BBC WorldwidePeter Capaldi in 'Doctor Who: Twice Upon a Time'
As we know, Capaldi said yes like a shot when Steven Moffat offered him the chance to replace Matt Smith, going on to play the Doctor for four years.
But he'd previously turned down the chance to audition for the aforementioned 1996 TV film. Why would Capaldi, a self-professed Doctor Who fan, do such a thing? Well, it turns out he was just too much of a fan.
"I knew I wouldn't get it," he explained back in 2014. "I loved the show so much that I didn't want to have anything to do with it, unless it was going to be me [definitely playing the part].
"I didn't want the disappointment [after] going through all the palaver - jumping through hoops for something I would never get."
At the time, Capaldi feared he was not established enough to be taken seriously as a contender. "It was an American pilot and I knew they would go for somebody who was well-known - which Paul was, and he was fantastic.
"So I said to my agent, 'Thank you very much, but I don't want to go along'."
Still, it all worked out in the end. Time's funny like that.
Related: Which classic Doctor Who monsters are most likely to return [Digital Spy]
Want up-to-the-minute entertainment news and features? Just hit 'Like' on our Digital Spy Facebook page and 'Follow' on our @digitalspy Instagram and Twitter account.