Doctor Who Season 13: Slowed-down finale montage teases 4 major clues

The Season 12 finale of Doctor Who called everything we thought we knew about the backstory of The Doctor into question. The game-changing episode included a scene that flashed through all 13 manifestations of the Doctor, and it's jam-packed with references that can be easy to miss. We've plucked out four of the most startling Easter eggs from the montage, and we're dissecting what they could mean for Doctor Who Season 13.

Major spoilers ahead for Season 12, episode 10 of Doctor Who, "The Timeless Children."

During the season finale, the Doctor learned that some of her earliest memories were implanted in her mind and not truly hers. However, thanks to some help from Ruth Doctor, she managed to use her recent memories to escape The Master's confinement in The Matrix. This memory montage appears as a kind of "Greatest Hits" of Doctor Who, showing the faces of companions and villains and all thirteen manifestations of the Doctor - plus some bonuses.

The sequence goes by in seconds, it's difficult to comprehend everything. Thankfully, some intrepid Whovians have uploaded the scene to YouTube in slow motion for our dissecting pleasure.

Now that you've had the chance to relive the scene for yourself, here are the moments we just can't get out of our heads.

4. The Sisters of Plenitude

"Cat-nuns" were one of the weirder additions to the Doctor Who universe. These feline Catholics lived in New New York City on New Earth, using human clones to develop medical techniques and cures way beyond their time, euthanizing the clones when they got too ill. The clones were freed by The Doctor, and the nuns arrested.

Their appearance in the montage is puzzling: They weren't malicious, just unethical, and had no intent on taking over the galaxy like the Daleks or Cybermen. This callback may suggest that we'll see more catkind in the future. The Sisters of Plenitude were not the only catkind on the show; other episodes set in the same distant future timespan feature the race as well.

3. The Rani

After the montage flips through the past Doctors, it goes through past enemies including The Rani. The Rani is a Time Lady established to be about The Doctor's age. Thanks to the sudden jumbling-up of The Doctor's backstory, this can no longer be true, so The Rani's origins are even more confusing than before.

One of the few other Gallifreyans the show has introduced, she's only appeared in three episodes thus far. Maybe she's due for a return in Season 13, with a brand new face.

3. Clara Oswald

We see nearly every friendly face the Doctor has traveled with since 2005: Bill, Amy, Rose, Martha, Donna, Wilfred, and River Song. Sarah Jane Smith, a Fourth Doctor companion who returned to the rebooted franchise and even had her own spinoff from 2007 to 2011, also makes an appearance.

Surprisingly, Clara Oswald is also part of this montage, despite the cryptic way she left the series. It was unclear how much of Clara The Doctor remembered. Her death meant the Time Lord had his memories of her wiped completely, though she did make a handful of appearances after that. Her appearance in the company of other companions means the Doctor rightfully considers her one of the lucky few to travel with him.

4. Morbius Doctors

This Easter egg answers a 44-year mystery: in 1976, the Fourth Doctor adventure "The Brain of Morbius" saw the Time Lord engaged in a battle of wits. Something similar to the Matrix scene happens here: The Doctor's past iterations flash on-screen, from the Third Doctor, to the Second, the First, followed by eight never-before-seen faces, interpreted as previous regenerations from the period prior to the television series.

Fans have struggled to bring this in line with canon: the "Morbius Doctors" meant the usual limit of 12 regenerations didn't apply to The Doctor for some reason. We now have that answer, thanks to the Season 12 finale: As the Timeless Child, these limits didn't affect the Doctor, just the Time Lords who came after. It only took nearly five decades, but Doctor Who managed to bring something from the old series into compatibility with canon, even though most of the other Gallifreyan lore was rendered invalid.

Doctor Who will return in late 2020.