regeneration is the secret of its longevity. Regeneration allows the show to switch lead actor, and it usually serves as something of a reset as well. In the modern era, showrunners usually time their departures alongside a regeneration, allowing their replacement to start with a clean slate.
Naturally, that means fans are eagerly invested in the idea of multi-Doctor stories. These Doctor Who team-ups are usually viewed as events in their own right and are frequently timed for anniversaries. They're an opportunity for fans to see their favorite Doctors side by side, to recognize the similarities and celebrate the differences. They're also tremendous fun because a good multi-Doctor story typically involves two or more Doctor-sized egos coming into collision.
Of course, Doctor Who is more than just a TV series. It's now something of a transmedia franchise in its own right, embracing everything from audio-dramas to comic books. Some of the earlier material isn't really considered canon anymore, but the excellent Big Finish audio-dramas and Titan's superb comics tend to be considered canon by fans.
The Three Doctors
The first ever multi-Doctor story was "The Three Doctors," and it united Jon Pertwee and Patrick Troughton with an ailing William Hartnell. The Time Lords were threatened by the return of Omega, the first Time Lord, who had been trapped inside the event horizon of a black hole. Omega was attempting to return to this universe, and to that end he was draining all the power of Gallifrey. The desperate Time Lords used the last of their power to draw multiple incarnations of the Doctor into play, and soon the Second and Third Doctors had leaped into the unknown, transported inside the black hole's singularity. The First Doctor served only as an adviser, a necessary adjustment to the plot driven by Hartnell's health.
The Five Doctors
Generally considered Timeless Child retcon adds a new level of depth to "The Five Doctors," revealing just how foolish and misguided Borusa really was.
The Two Doctors
"The Two Doctors" was the last multi-Doctor story of classic Doctor Who, and unfortunately it's also the worst. This story brought together Patrick Troughton's Second Doctor and Colin Baker's Sixth Doctor, and the script is nowhere near so tight and effective. The showrunners were attempting to give the Doctor something of an edge, but unfortunately that backfired badly, leading him to become utterly unsympathetic as a character. Unfortunately that effect is backdated through this multi-Doctor arc, leading the Second Doctor to appear frankly racist. It's not even possible to easily figure out how it fits with the show's own continuity; the Second Doctor is somehow aware his companions had their memories of him erased, but that should have happened right before his regeneration.
Time Crash
The first multi-Doctor story of the Doctor Who relaunch was actually a Children In Need special, a mini-episode written by Steven Moffat. It was just a bit of fun, an opportunity to get Peter Davison's Fifth Doctor and David Tennant's Tenth Doctor in the TARDIS together. After initially clashing - the Fifth Doctor assumes the skinny rake in front of him is just a fan who's somehow gotten into the TARDIS - the two bond. Amusingly enough, these two Doctors are now far more closely connected. Tennant married Peter Davison's daughter, Georgia Moffett.
The Day of the Doctor
The 50th anniversary Doctor Who special, "The Day of the Doctor," was easily the most spectacular story in the show's history. It's primarily a celebration of the Doctor Who relaunch, particularly focused on the end of the Time War, and it brought together David Tennant and Matt Smith's incarnations of the Doctor. It also introduced John Hurt as the War Doctor, a forgotten incarnation of the Time Lord who was responsible for Gallifrey's destruction. There's something joyously optimistic about "The Day of the Doctor," with the Doctors combining their intelligence to save their homeworld of Gallifrey. It was an unalloyed success, introducing new viewers to the idea of multi-Doctor stories.
Twice Upon A Time
The 2017 Doctor Who Christmas special was Peter Capaldi's final outing as the Doctor, and he went out in style. The Twelfth Doctor was refusing to regenerate, reluctant to allow his adventure to end. The TARDIS took him back to the North Pole in 1986, where he encountered his first incarnation, who was facing exactly the same issue. Unlike other multi-Doctor stories, this one is more character-driven; it shines a light on the similarities between the First and Twelfth Doctors and leads both to the point where they are willing to let themselves go. This time David Bradley plays the first Doctor, having portrayed William Hartnell in the docudrama An Adventure in Space and Time.
Fugitive Of The Judoon
The most unexpected multi-Doctor story of all was "Fugitive of the Judoon," in which Jodie Whittaker's Thirteenth Doctor stumbles upon another mysterious incarnation. Played by Jo Martin, this Doctor appears to be a pre-Hartnell Doctor, given she shares Hartnell's habit of calling the TARDIS her "ship" and doesn't know what the sonic screwdriver is. However, her TARDIS was already fixed in the shape of a police box, suggesting the truth may be a lot more complicated. "Fugitive of the Judoon" set up the Timeless Child retcon, which revealed there is no limit to the Doctor's ability to regenerate.
The Time Lord Victorious Transmedia Story Features Multiple Doctors
"Time Lord Victorious" is a phenomenal transmedia initiative that sees the Eighth, Ninth, and Tenth Doctors collide in the Dark Times when the universe was young. It all begins when David Tennant's Tenth Doctor goes too far, attempting to rewrite the timeline and prevent death ever becoming a force in the cosmos. The transmedia stories span a number of novels, audio dramas, and comics.
Big Finish Audio-Dramas Have Featured Multiple Doctors
Big Finish has been producing high-quality Doctor Who audio-dramas for over 20 years now, frequently recruiting of the cast to serve as voice actors. Over the years they've released a number of superb multi-Doctor adventures, often featuring the Doctors themselves. Here are all the audio-dramas to date:
- "The Sirens of Time" was the first story in Big Finish's monthly range, and it united three Doctors - Peter Davison's Fifth Doctor, Colin Baker's Sixth Doctor, and Sylvester McCoy's Seventh Doctor. The stakes are phenomenally high, with Gallifrey itself threatened and the web of time itself in danger.
- "Project Lazarus" featured Colin Baker as the Sixth Doctor and Sylvester McCoy as the Seventh Doctor. It's part of an ongoing series exploring a cosmic location called the Forge.
- "The Four Doctors" was a bonus story for subscribers, bringing together Peter Davison, Colin Baker, Sylvester McCoy, and Paul McGann as their respective incarnations of the Doctor. The Daleks unleash a dangerous temporal maelstrom that tests all four Doctors to their limit.
- "Peri and the Piscon Paradox" is focused on Peri, one of the Doctor's companions and attempts to resolve some of the continuity problems surrounding the character. It's a complex story, featuring Peter Davison and Colin Baker.
- "Destiny of the Doctor" was a fascinating event designed to celebrate Doctor Who's 50th anniversary. It featured Matt Smith's Eleventh Doctor sending instructions for his past selves back in time.
- The 50th anniversary celebrations also included "The Light at the End," an ambitious story featuring no less than eight Doctors. It debuted William Russell as the First Doctor, Fraser Hines as the Second Doctor, and Tim Treloar as the Third Doctor.
- Tom Baker's Fourth Doctor collided with his second incarnation in "Return to Telos," a story set around the classic Patrick Troughton adventure "Tomb of the Cybermen."
- Adapted from Lance Parkin's novel, "Cold Fusion" united the Fifth and Seventh Doctors in the face of a crisis involving the Earth Empire. The canonicity is a little uncertain, as some of the dialogue contradicts the Timeless Child retcon.
- In "The Eye of the Storm," the Sixth and Seventh Doctors find themselves working with Professor River Song in the year 1703.
- "The Legacy of Time" was a massive crossover event that celebrated 20 years of Big Finish Doctor Who audio-dramas. With time collapsing, different incarnations of the Doctor found themselves working with friends and companions from different points in their personal timestream. The Third, Fourth, Fifth, Sixth, Seventh, and Eighth Doctors were ultimately forced to work together to save all of time and space.
- "Daughter of the Gods," in which the TARDISes of the First and Second Doctors collide. This story is set during the events of "The Dalek Masterplan," a story in which the Daleks pursued the Doctor through time and space.
- "Out of Time" brings together the Fourth and Tenth Doctors in a fascinating battle with the Daleks, in which each Doctor is shaken by their encounter with the other.
- "The End of the Beginning" unites the Fifth, Sixth, Seventh and Eighth Doctors in an attempt to save the universe from an ancient Time Lord weapon.
Doctor Who Comics Have Featured Multiple Multi-Doctor Stories As Well
Modern Doctor Who comics are published by Titan Comics, and they include some phenomenal multi-Doctor stories as well. In theory, the comic book medium is perfect for this kind of story because Titan doesn't need to recruit actors. In reality, however, the publisher shows an irable degree of caution with Doctor Who team-ups, perhaps to avoid losing their uniqueness. Here are the multi-Doctor stories to date:
- "Prisoners of Time," a 50th anniversary celebration event that featured the first eleven Doctors.
- "Four Doctors" was another major event, a miniseries featuring David Tennant's Tenth Doctor, Matt Smith's Eleventh Doctor, and Peter Capaldi's Twelfth Doctor. It marked Titan's debut of John Hurt's War Doctor as well.
- "Vortex Butterflies" was published in The Tenth Doctor Season 3 #6, a brief encounter initiated by Peter Capaldi's Twelfth Doctor. He summoned the Tenth Doctor to give him a warning to pay more attention to the TARDIS.
- "The Lost Dimension" was a spectacular crossover event featuring the first twelve Doctors. The opening of a cosmic phenomenon called a white hole wreaked havoc in time and space, and the Doctors were all soon caught up in it - along with the Doctor's daughter, Jenny.
- "A Little Help From My Friends" is the latest multi-Doctor story. Technically set during the events of "Blink," it sees the Thirteenth Doctor and her fam arrive in 1969. There, they cross paths with the time-lost Tenth Doctor and Martha, who've been transported there by the Weeping Angels. The two Doctors are forced to work together against the combined forces of the Weeping Angels and the Nestene Consciousness.