The 50th anniversary of Doctor Who is upon us. On November 23, 1963 -- the day after John F. Kennedy and C.S. Lewis died -- the story of the renegade Time Lord of Gallifrey began. This Saturday, in honor of the occasion, fans will get a worldwide simulcast event of the long-anticipated 50th anniversary special, "The Day of the Doctor." Over the years, the Doctor has experienced numerous lives and incredible adventures ranging from the tragic to the sublime. But what about all the rejected stories? What about the things that were too risky or strange, even for Doctor Who? Here are some plans and adventures that are sure to fire up the "what if" machines in the brains of Whovians everywhere. Matt Smith and David Tennant Wanted to Be the Doctor... Together According to Steven Moffat in an interview with Radio Times, former Doctors Matt Smith and David Tennant had so much fun filming the 50th anniversary special together that they discussed how their team-up could continue for a whole new season. After all, an anniversary isn't necessary for multiple Doctors to meet on-screen, as proved in the 1985 story "The Two Doctors" and the 2007 mini episode "Time Crash." According to Moffat, "Matt told me he'd worked out this plan that they'd both continue in Doctor Who, do five individual episodes each and three together – would that be OK? It was a nice plan. I think if I'd said yes, they'd have gone for it." This idea, tragically, seems like it is not to be, with the upcoming Twelfth Doctor about to claim the title. All images courtesy BBC

Doctor Who and His Companions Were All Originally Scientists Doctor Who's creator, Sydney Newman of the BBC, conceived of a family-friendly, science-fiction adventure show that would allow for stories of various genres. A group discussion in the BBC serials department then led to a pitch that wasn't about a Time Lord and his companions, but rather three "scientific troubleshooters, established to keep scientific experiments under control for political or humanistic reasons." The specialists worked together in a futuristic HQ/lab and were described individually as "Handsome Young Man Hero," "Handsome Well-Dressed Heroine Aged About 30" and "Mature Man, 34-40, with some character twist." Newman didn't care for the idea and didn't think it would entertain children as well as adults. He did like the idea of the "Mature Man," though, picturing an old scientist with strange and mysterious qualities. Newman reimagined this character as an amnesiac alien who had lived for centuries and had recently escaped from his planet in a space ship that was bigger on the inside. Unaware of his name but remembering that he was a scientist, this "senile old man" would use the alias "Dr. Who." Later on, the production team decided to simply call him "The Doctor."

Doctor Who Almost Didn't Have Monsters When Doctor Who first went into production, creators Sydney Newman and Donald Wilson both agreed there would be "absolutely no bug-eyed monsters." Then it turned out the second story, already written by Terry Nation, would feature a race of deadly alien monsters. Angry, Newman and Wilson demanded the story be scrapped and replaced. But Verity Lambert, *Doctor Who'*s co-creator and first producer, didn't concede. She argued that these weren't one-dimensional monsters and the story would strike a chord with British audiences, speaking to the dangers of prejudice and recalling the evil of Nazi Germany. This was a morality tale from which children would benefit. Besides, she pointed out, the monsters and sets were already being made and scrapping the story for a new one would seriously delay filming. Lambert won the argument and the second Doctor Who adventure introduced the now-legendary menace of the Daleks. Ratings soared and Britain embraced what the news media called "Dalekmania." The Daleks were credited with making the show a mainstream success. They started appearing in more TV adventures, as well as comic strips, theatrical films, and their own stage play. Without Terry Nation's story and Verity Lambert's argument, Doctor Who might never have become a show about a hero fighting monsters. Who knows if it would've lasted?

The Doctor Could Have Been a Woman -- And Still Might As actor Tom Baker prepared to leave the TARDIS in 1981 after seven years as the Doctor, he was asked what kind of man the next Doctor might be. Baker responded that the next incarnation didn't necessarily have to be a man at all. Sydney Newman, initial creator of Doctor Who, not only thought it was possible to make the hero a woman but tried to make it to happen in 1987. Newman was asked by the BBC for suggestions on revising the show to revive interest. In his memo to the BBC, Newman suggested certain changes that he would make if he returned as producer. First, the Doctor would travel with two siblings, a 12-year-old girl and an 18-year-old boy. After spending a couple of adventures with the alien hero and getting used to him, circumstances would lead the Time Lord to regenerate into a woman. The show could then explore the children adjusting to the fact that their friend was different now, while the Doctor (typically) didn't see what all the fuss was about. If this plan had been adopted, Newman would have replaced John Nathan-Turner as the show's producer and Sylvester McCoy would not have been the Seventh Doctor. Who knows how different the last years of classic Doctor Who would have been? The possibility of casting a woman still comes up nearly every time it's time for the Doctor to regenerate. Science fiction often allows modern audiences to examine the social flaws of both the past and the present; having a female form could provide new challenges for the Doctor when visiting planets and historical periods where people would dismiss or fear an educated woman with the knowledge and authority of a Time Lord.

Regeneration Was Originally a Cosmic Prank After original producer Verity Lambert left Doctor Who, William Hartnell – the original Doctor -- had increasing concerns over the show's direction and atmosphere. New producer John Wiles and script editor Donald Tosh suggested writing Hartnell out of the program in a story titled "The Celestial Toymaker." In it, the titular villain who wields cosmic abilities forces the Doctor and his companions to play his strange games. As originally written, the Toymaker makes the Doctor invisible and later restores the hero's visibility, but has the last laugh by giving him a different appearance. Unable to restore himself, the new Doctor then goes off in the TARDIS and continues his adventures. But others protested recasting Hartnell, and the BBC resisted the decision. Wiles and Tosh left Doctor Who before "The Celestial Toymaker" was completed, and the story ended differently. Problems continued between Hartnell and the new show runners; when his contract ran out, he was indeed recast. This time however, the change was called "renewal" (later "regeneration") and was embraced by the Second Doctor as a natural part of life for his people, a "gift" that was necessary for survival. If the original plan had gone through and the Second Doctor had been the result of an enemy playing a joke on the hero, the regeneration mythology that has given us generation after generation of new actors in the role of the Doctor might never have become a part of the show. In the 1960s, viewers weren't used to recasting heroes the way today's audiences are, and Doctor Who may not have kept up its momentum to continue into the Third Doctor's era.

The Thirteenth Doctor Was Almost a Villain In Colin Baker's final episodes as the Sixth Doctor, he encounters a sinister Time Lord called the Valeyard, played by Michael Jayston. Eventually, the Master reveals that the Valeyard is actually a physical manifestation of the hero's dark side, somehow created in a possible future when things go wrong during the Doctor's regeneration into his thirteenth body. The Valeyard was defeated and hasn't been on-screen since, though he has been explored further in tie-in media and was referenced in the recent episode "The Name of the Doctor." Big Finish Productions is releasing an audio play featuring his return (with Jayston reprising the role) and revealing more about his character. Originally, the Valeyard wasn't meant to be the Doctor's dark side incarnate. An earlier draft of the story "The Ultimate Foe" stated clearly that the Valeyard was quite simply the Doctor's thirteenth incarnation. The idea was that by this time in his future, the Doctor was corrupt, hungry for power and obsessed with finding a way to live past the Time Lord limit of thirteen bodies. But then producer John Nathan-Turner argued with Eric Saward that he didn't want to have the Doctor's future set in stone as a man who becomes a villain. Following the argument, Saward left Doctor Who. Writers Pip and Jane Baker then revised the story.

The Doctor Almost Met Both Death and the Devil For years, fans wanted to know if it was possible for different Doctors to meet via time travel. The production team always said no, but then the show's 10th anniversary came in 1973. To celebrate this, producer Barry Letts wanted the Third Doctor to join forces with his previous two incarnations in order to save all of Time Lord society from a strange menace. The resulting story was "The Three Doctors." But originally, a very different tale was planned, called "Deathworld." This story introduces the powerful Federation of Evil, an army of monsters ready to destroy the Time Lords, led by an avatar of Death itself. To avert war, the Time Lords send the Third Doctor and his previous incarnations (above) to the Federation's native realm of Underworld. There, they fight zombies, mythological creatures, the Hindu goddess Kali, and the Four Horsemen of the Apocalypse. Eventually, Letts decided that the story was just too bizarre, even for Doctor Who, and it was scrapped. Similarly, the Doctor almost met the Devil during the 1970s, in a pitch for a Doctor Who film titled "Doctor Who Meets the Scratchman." The Scratchman, a name referencing the Devil, was a powerful entity delighting in evil and destruction. The script saw him unleashing chaos on Earth that included Cybermen rising from the sea, living scarecrows, and the Doctor getting imprisoned inside a giant pinball machines where each gaping hole was a gateway to Hell. Actor Tom Baker said that he liked the story, remarking that it was "a very violent film, but very funny too." However, the production office hated it and the story was rejected.

A U.S. Reboot of the Show Could Have Erased Its History The 1996 Doctor Who TV-movie that introduced Paul McGann as a new iteration of the Doctor was also intended as a backdoor pilot; if it had done better in the U.S., an ongoing series would have followed. Originally, the idea was to reboot the mythos from scratch rather than revive it. McGann wouldn't have been the Eighth Doctor then, but the new First Doctor. There were several drafts of the reboot program in which the Doctor was a half-human Time Lord, the product of a woman from Earth and a Gallifreyan named Ulysses (who was also known in history as Blackbeard the Pirate). The Doctor and the Master were half-brothers and part of the royal line of Gallifrey. After taking power, the Master decides to have the Doctor killed so the hero can't threaten his reign. Escaping for his life and deciding he needs to find his missing father, the Doctor steals an old TARDIS, which becomes a living ship after its circuits are inhabited by the ghost of the hero's grandfather Borusa. One of the major reasons behind this reboot origin was to give the Doctor a quest rather than the open-ended idea that he traveled simply because he enjoyed exploring. Making him half-human likewise gave him a direct reason to protect Earth beyond simply being fond of it. There were other proposed changes as well: the Daleks were re-imagined to have mechanical spider legs and now served the Master; the Cybermen were not creatures that discarded individuality, but rather vain cyborgs called the Cybs who had names and kept a Cyber Dog; and instead of seeming endless, the TARDIS interior would have only five rooms. Another draft even gave the Doctor a bulldog named Winston (after Churchill).

Time Lords Were Almost Asexual Andrew Cartmel was the final script editor on the classic Doctor Who program before it was canceled in 1989, and came up with what has been widely called the "Cartmel Masterplan." Working with writer Marc Platt, Cartmel wanted to uncover the Doctor's secrets in a story called "Lungbarrow" (the same name as the house the Doctor grew up in). The Doctor would be revealed as the reincarnation of one of the founders of Time Lord society and Gallifreyans would be revealed as sterile beings who procreated asexually with biological looms. There were no fathers, mothers or children, only "cousins." In addition to all this, the hero's young companion Ace would become the first human Time Lord. However, producer John Nathan-Turner decided against this plan as it revealed too much of the Doctor, and he wasn't sure the audience would respond well. There was debate on whether some of the revelations were truly in keeping with the characters and the program. "Lungbarrow" was reworked into a story called "Ghost Light" and the Doctor Who program was cancelled soon after. In the modern Doctor Who show, Russell T. Davies and Steven Moffat deliberately contradicted some of the Cartmel Masterplan by having the Doctor confirm that he was a father and grandfather, rather than an asexual being.