It’s official: Peter Capaldi’s Twelfth Doctor will be regenerating this season on Doctor Who. Change is never easy, but to help you get ready, here is a look back at every one of the Doctor’s past regenerations.

The Doctor’s first regeneration occurred in the 1966 serial The Tenth Planet. The concept was created so that Second Doctor Patrick Troughton could take over the role for an ailing William Hartnell.

The 1969 story The War Games not only showed the Doctor’s second regeneration, it also introduced the Doctor’s homeworld Gallifrey and the Time Lords. And while Patrick Troughton left the show, his replacement, Jon Pertwee, wasn’t cast until after the story aired.

Pertwee’s final turn as the Third Doctor occurred in the 1974 story Planet of the Spiders, and it was also the first time the term “regeneration” was mentioned onscreen.

Tom Baker’s seven-year tenure as the Fourth Doctor established that the Doctor could only regenerate 12 times. So when Baker regenerated into Fifth Doctor Peter Davison in the 1981 story Logopolis, the Doctor was one step closer to the end.

Davison’s time as the Doctor came to a close in the four-part story The Caves of Androzani (1984), which to this day is still voted as one of the best classic Doctor Who stories.

When Colin Baker’s era was cut short in 1987, the Sixth Doctor refused to film his regeneration scene. Instead, Seventh Doctor Sylvester McCoy wore a blonde wig, and his face was briefly obscured by the regeneration energy.

In 1996, Fox and the BBC attempted to revive the show with a back-door pilot. Rather than reboot the series, unprecedented for the time, the producers chose to continue the original series, bringing back McCoy to film his regeneration into Eighth Doctor Paul McGann.

While the pilot proved unsuccessful, McGann continued to play the Doctor in audio dramas produced by Big Finish. It wouldn’t be until the 2013 mini-episode The Night of the Doctor that McGann would return to the screen, regenerating into the previously unknown “War Doctor” played by John Hurt. Hurt’s own regeneration into Christopher Eccleston’s Ninth Doctor occurred shortly after in the 50th Anniversary special The Day of the Doctor.

Eccleston’s turn proved successful when the series was rebooted in 2005, but the actor chose to leave after only one season and was replaced with David Tennant’s Tenth Doctor in the episode “The Parting of Ways.”

In 2009, during the two-part story “The Stolen Earth”/”Journey’s End,” a mortally wounded Tenth Doctor used his regeneration to heal himself — but for the first time, stopped short of changing his appearance.

It would be just one year later, in 2010, that Tennant would fully regenerate into Matt Smith’s Eleventh Doctor, in a story then executive producer Russell T. Davies had planned since Tennant had been cast.

With his regeneration cycle at an end, the Doctor prepared himself for death. But, after spending more than 900 years protecting the planet Trenzalore in The Time of the Doctor, he was granted a whole new regeneration cycle, allowing him to regenerate into Peter Capaldi’s Twelfth Doctor.

How do you think Capaldi’s Doctor will meet his end, and who should take his place? Let us know in the comments below.

Doctor Who Season 10 premieres April 15 at 9 p.m. on BBC America.

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