So, it's finally revealed who the Doctor's eccentric new snog-buddy is, and why she's so very familiar with him, and she's also revealed her latest plan for world domination. So all the Doctor has to do is figure out a cunning way to beat the Cybermen and foil Missy's plan, and if he can offer Clara the change to get her Danny Pink back, so much the better.

"Death in Heaven" contains all this, and so much more.

Here are a few things to keep an eye out for, the next time you watch:

(The episode is available on iTunes and Amazon.)

This was supposed to be Clara's last story. Jenna Coleman had announced her intention to leave Doctor Who at the end of Season 8, and so the script was written with this in mind. Then, after she had read the script for "Death in Heaven," Jenna asked if she could stay on for the Christmas Special — "Last Christmas" — and Steven Moffat agreed to write her finale in that episode instead, but being canny, he kept a different version where Clara remained with the Doctor.

He told Doctor Who Magazine: "She came to the read through and did the 'write out' version — and again changed her mind. But the truth is I never wanted her to go. And with Last Christmas, I'd already written the alternative version where she stayed, and I preferred that version. Frankly, I didn't want to lose her. She's an amazing actress, and she never stops working to make Clara better. I was very happy to go the extra mile to make sure we could keep her."

Possibly as a tribute to the departing/not departing Clara, and as a nod to her claim in "Dark Water" that she is the Doctor, the title credits for this episode were altered so that Jenna Coleman's name appeared before Peter Capaldi's, and Jenna's eyes appeared in the swirling animation, rather than Peter's. It's the only time anyone other than the Doctor has appeared in a title sequence, apart from a fleeting sight of the Master's eyes in the title sequence for the 1996 Doctor Who TV movie.

Even by Doctor Who standards this story is jam-packed with British comedy talent. Michelle Gomez we know about, but there's also Chris Addison playing Seb. A stand-up comedian and actor who is probably best known to British TV audiences from the political panel show Mock the Week, and his role as the hapless Ollie Reeder in the political comedy The Thick of It (also starring Peter Capaldi):

https://www.youtube.com/watch?v=f1Dq_aINJ9U

He's joined by Sanjeev Bhaskar, who plays Colonel Ahmed. Sanjeev is best known to British viewers as one of the creators of the sketch show Goodness Gracious Me, and he's the third member of the cast of that show to make an appearance in Doctor Who, after Meera Syal (Dr. Nasreen Chaudhry in "The Hungry Earth" / "Cold Blood") and Nina Wadia (Dr. Ramsden in "The Eleventh Hour"). Keeping up with the medical achievements of his former colleagues, Sanjeev also played Dr. Avishka Sangakkara in the Big Finish Doctor Who audio stories "The Eight Truths" and "Worldwide Web:"

https://www.youtube.com/watch?v=z6h0lkq-Sno

Kate Stewart throws down an older Cyber head, with the stern words "You left this behind on one of your previous attempts..." This is a continuation of the references to the 1969 adventure "The Invasion", in which the Cybermen arrive in London, particularly the area around St. Paul's Cathedral, only to be thwarted by the Second Doctor and Brigadier Lethbridge Stewart, Kate's father.

Kate's claim that the Doctor is still "on the payroll" must be something of a surprise to her Time Lord chum, given that he had been offered a salary by the Brigadier back in his Third Incarnation, but he turned it down in favor of a lab to work in and a car. He even said: "Money? My dear chap, I don't want money. I've got no use for the stuff!"

As revealed by Missy, Gallifrey's galactic co-ordinates—"10-0-11-00:02"—were originally revealed by the Fourth Doctor to Sutekh, in the story "Pyramids of Mars". Sutekh does not recognize Gallifrey by name, but is familiar with the planet only by its "binary location from galactic zero centre."

https://www.youtube.com/watch?v=uPjJ_VAubRs

Danny's body is taken to the Chaplet Funeral Home, which has to be a joke in the direction of the First Doctor's companion Dodo Chaplet, based on the expression "dead as a dodo."

There's another nod to the Second Doctor as Missy playfully uses the phrase "oh my giddy aunt" while enacting her plan to kill Osgood. As a keen student of the Doctor's various incarnations, Osgood will have recognized the phrase as one he used often.

The Doctor refers to the Valiant - last seen in "The Sound of Drums" - as "Cloudbase," starting a conversation about whether this fictitious space station came from the Gerry and Sylvia Anderson puppet science fiction series Thunderbirds, or from their equally popular series Captain Scarlet and the Mysterons. Cloudbase is the fictional skyborne headquarters of the international security organization Spectrum.

https://www.youtube.com/watch?v=NAzoV0-Scgo

10 Things You May Not Know About ‘Last Christmas’

Now go back and read the entire 10 Things You May Not Know About Doctor Who archive.