Doctor Who is one of the longest running TV shows in the world, with a history that stems back all the way to 1963. There are many reasons why the British sci-fi drama has lasted so long, one of them being the concept that The Doctor and his/her companions can travel anywhere in time and space, giving nearly unlimited settings and scenarios for our heroes to become entangled with.

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Another reason why the show has persevered is the concept of regeneration. When mortally wounded, or otherwise on the brink of death, a Time Lord can rejuvenate every cell in their body, altering their appearance. This allows the show to hand off the character to a new actor so that The Doctor's adventures can continue to be enjoyed for generations to come. Here are all the canonical series regenerations, ranked.

Colin Baker To Sylvester McCoy (1987)

The late 1980s were not kind to Who. The curious decision to have Colin Baker portray a darker, slightly meaner Doctor but to dress him like a children's TV clown clearly wasn’t working. Ratings were dropping and it was time for a change.

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After being fired from the role, Baker refused to return to film a regeneration sequence. So, what we get is Sylvester McCoy in A Colin Baker wig and his back turned to the camera. Ridiculous effects show the TARDIS being shot down to a planet (by a rainbow!?) and the Doctor’s enemy The Rani boards the iconic ship.

Patrick Troughton To Jon Pertwee (1969)

The change from Troughton To Pertwee marked the end of the show's black-and-white era. After being put on trial by the Time Lords, the Doctor is banished to 20th-century Earth. In reality, this was done the save some of the show's budget. Technicolor isn't cheap!

On top of the banishment, the Time Lords also forced to Doctor to “change his appearance” (the term 'regeneration' wouldn’t be used until later in the series). They gave the Doctor a choice of faces, which he refused because they were “too fat” or “too thin,” so they made the choice for him and sent him spinning into the dark void, utterly confusing viewers.

David Tennant To David Tennant (2008)

In the episode "The Stolen Earth," The Doctor is mortally wounded by a Dalek. He manages to make it back to the TARDIS, only to be forced into a surprise regeneration, ending the episode on a cliffhanger!

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But it turned out that everybody was getting excited over nothing. The Doctor transferred his regeneration energy to a severed hand he lost during his first episode as his 10th incarnation. This made him retain his DNA and his appearance, and thousands of fans around the world were unimpressed by the cheap trick.

John Hurt To Christopher Eccleston (2013)

The War Doctor, played by acting icon John Hurt, returns to his TARDIS and begins his regeneration into the 9th Doctor, linking the gaps between the show's "Classic" era and the modern series.

This reason this one ranks so high on the list is that Eccleston refused to return to film the scene, and we don't see the full process.

Peter Davison To Colin Baker (1984)

The 5th Doctor, unsure he can perform the mystical rejuvenation process, lays down on the floor of the TARDIS where he is haunted by visions of past companions. This gives the Doctor the strength he needs to regenerate into his sixth form.

A brilliant premise, let down by awful 1980s kaleidoscope effects and general cheesiness. The audience cringed, and poor Colin Baker never really recovered.

Tom Baker To Peter Davison (1981)

During the 4th Doctor’s final adventure “Logopolis,” The Doctor ascends a radio tower to stop The Master’s universe-conquering threats, which he plans to broadcast to the entire galaxy. The Doctor is successful in ending quite possibly the most ambitious podcast of all time, but falls to his death in doing so.

The result is a bizarre frame fade effect, where Tom Baker transforms into a papier-maché face, which transforms into Peter Davidson covered in baby powder, before finally settling on Davison and the Doctors next guise.

Paul McGann To John Hurt (2013)

When Doctor Who returned to our screens in 2005 following a 9-year gap, the original series and lore were barely referenced, with an only handful of old villains and flashbacks spread out here and there. All we really knew about the period between was that there was some kind of devastating “Time War” between the Daleks and the Time Lords.

In the short “Night Of The Doctor,” The Doctor is given an elixir by The Sisterhood Of Karn, which will force him into a controlled regeneration in which he can choose his characteristics. As this is during the much fabled Time War, he decides the universe doesn’t really need a Doctor any more and so he chooses the identity of a warrior and the darkest time of the Doctor’s history begins.

Christopher Eccleston To David Tennant (2005)

The first regeneration of the revamped Who. After a battle with The Daleks, the Doctor realizes he must regenerate but he puts on a brave face in order not to scare his new companion, Rose Tyler.

His constant reassurances to Rose, whilst saying goodbye to his “daft old face,” are enough to bring a tear to any hardened fan's eye. This was the first time we saw the 'firework' effect, which would end up becoming a mainstay of the process.

Matt Smith To Peter Capaldi (2013)

By this point, the 11th Doctor had run out of regenerations, finally confirming that he only has 12, a rule set by the series before the 2005 reboot.

Dying of old age and weakened from fighting those dastardly Daleks once again, the surviving Time Lords grant the Doctor a new regeneration cycle through a crack in time and space. Smith gets plenty of time to say goodbye to his companion Clara, in another heartfelt scene.

Sylvester McCoy To Paul McGann (1996)

Easily the most violent entry on the list. Back in 1996, the BBC decided to try and reboot Doctor Who with a TV movie aimed to attract American audiences, in which the 7th Doctor was gunned down by a gang on the mean streets of New York!

Believed dead and taken to the morgue, the Doctor's physique painfully contorts from McCoy to McGann in a chorus of blue lightning flashes.

Jon Pertwee To Tom Baker (1974)

The first regeneration in color, and one that sticks in the hearts and minds of the older generation as it heralded the appearance of the most iconic Doctor.

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Falling out of the TARDIS after a battle with the Spider Queen and into then companion Sarah Jane’s arms, Pertwee triggers his change with his heartwrenching farewell line. “A tear, Sarah Jane? Now don’t cry, while there is life, there is…” The 3rd Doctor fades before finishing his sentence. This one is still a real tear-jerker!

Peter Capaldi To Jodi Whitiker (2017)

After a clash with the Master, Missy and the Cybermen, losing his companion Bill in the process, The 12th Doctor refuses to heal himself.

That is the set-up to the 2017 Christmas special, Capaldi’s final episode where the 12th meets up with 1st (played by David Bradley) who is about to undergo his first regeneration (more on that in a moment). It’s a wonderful study and celebration of the character, written by Stephen Moffat, life-long fan of the franchise himself.

David Tennant To Matt Smith (2010)

Arguably the most popular Doctor of this generation, 10's demise came at the hands of a woefully unaware Wilfred Mott, played wonderfully by British legend Bernard Cribbins.

This was not only Tennant’s last episode but also that of showrunner Russell T. Davis, who brought the series back from oblivion in 2005. Knowing that time is short after absorbing a deadly amount of radiation, the Doctor decides to travel through time to check in on those characters that meant so much to him during his tenure.

William Hartnell To Patrick Troughton (1966)

The very first regeneration rightfully tops our list. Effects-wise, it still holds up today. What an achievement!

The 1st Doctor, played by William Hartnell, succumbed to his fate by simply surrendering to his old age. Unlike pretty much all of the original Doctor Who regenerations (and some of the new who ones too), which have fallen victim to dated effects, Hartnell to Troughton is just a brilliant white light which glows to a seamless transition between the two actors.

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