"The Name of the Doctor" is a many-faceted story, it's sharply comic, it's eerie and atmospheric, and it contains enough nods to the history of Doctor Who — recent and classic — to cause many a spontaneous squeal from hardcore fans. It has to explain who Clara Oswald is, how she became the Impossible Girl, and set up Doctor Who's 50th anniversary special, "The Day of the Doctor."

It is also one of River Song's many grand finales, the last from her perspective (so far), although as far as the Doctor is concerned, the Singing Towers of Darillium are still a way into his future.

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

(The episode is available on iTunes and Amazon.)

The episode was trailed by two prequels. One, called "Clarence and the Whispermen" showed a conversation between the murderer Clarence and the Whispermen, top-hatted henchpersons of the Great Intelligence. In exchange for a reprieve of his death sentence, he is given interstellar coordinates to be handed to "the reptile dectective" at a subsequent date.

The second, "He Said, She Said" examines the internal monologues of Clara and the Doctor as they examine their feelings about each other:

https://www.youtube.com/watch?v=mtaIpkjF6Ss

Steven Moffat planned that the episode would end with the Doctor admitting that the time rift that represents his life leads directly back to the last day of the Time War, in order to set up the story within "The Day of the Doctor" in which the Eleventh and Tenth Doctors would confront the Ninth (who would at that point have been played by a returning Christopher Eccleston) about his part in destroying Gallifrey. Clara was to have emerged from the rift furiously upset with the Doctor for this act of genocide, and screaming that she knows who he really is. In the event, Eccleston's decision not to take part forced a rethink, and the introduction of the War Doctor.

Initially, Moffat considered reintroducing the Eighth Doctor (played by Paul McGann) as the architect of Gallifrey's downfall, but was more intrigued by events surrounding the 1983 20th anniversary special "The Five Doctors." As William Hartnell had died in 1975, the role of the First Doctor was given to Richard Hurndall, and his re-interpretation of the role was different enough in tone to lead Moffat to think about incarnations of the Doctor that we may not have seen. As he was already queasy about the idea of the Doctor being capable of the genocide of his own people, it made sense to consider two things, that the Doctor might not remember his part in the ending of the Time War correctly, and that there could be an incarnation that the Doctor refused to acknowledge.

https://www.youtube.com/watch?v=3Xx4NbPkHGM

One of the Doctor's thoughts about what he might do when he retires includes bee-keeping, which is, in a curious coincidence that is almost certainly intentional, exactly what Sherlock Holmes did when he retired.

The Great Intelligence mentions a few of the Doctor's less-flattering nicknames, and mentions the Valeyard. This is a reference to the 1986 series-long story arc, "The Trial of a Time Lord," in which the Doctor is the subject of a courtroom drama on Gallifrey, and his prosecuting counsel is a dark-robed figure called the Valeyard, who later turns out to be a future incarnation of the Doctor himself. Like the Dream Lord in "Amy's Choice," he represents the darker aspects of the Doctor's psyche, but where he appears in the Doctor's future is still unclear.

https://www.youtube.com/watch?v=Y2INBe_qZFo

The original stage directions for the Doctor's rescue of Clara were that he would carry her back out of the rift, but Matt Smith had injured his knee and was unable to walk while holding Jenna Coleman.

In order to show Clara (and the Great Intelligence) interfering with the Doctor's timeline, clips were taken from the show's 50-year history, with Coleman inserted into the background. These include:

The First Doctor - footage taken from "The Aztecs", dialogue taken from "The Web Planet"

The Second Doctor - footage from "The Mind Robber" and the 21st anniversary special "The Five Doctors"

The Third Doctor - footage from "The Five Doctors"

The Fourth Doctor - footage from "The Invasion of Time"

The Fifth Doctor - footage from "Arc of Infinity"

The Seventh Doctor - footage from "Dragonfire"

The Sixth Doctor was represented by a lookalike, although he (and all the other Doctors to date) can be heard in the collage of sounds coming from the Doctor's timeline.

https://www.youtube.com/watch?v=N34g5z4t168

It seems the Paternoster Gang, in order to fully enjoy the sensory realm of their conference call, enjoy the music of Vivaldi, in particular "Spring" from The Four Seasons. In a curious quirk of cultural history that Doctor Who fans may appreciate, it's actually fairly unlikely that people of the Victorian era will have been familiar with The Four Seasons, as it fell out of popularity in the late 1700s, only to be revived in the mid-1950s by an Italian group called I Musici.

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

This isn't quite the first time TV viewers have seen a TARDIS (or TARDISes) before the chameleon circuit has been engaged. In "The War Games," the Second Doctor's companions Jamie and Zoe were returned to their own timestreams in TARDISes that were tall black boxes, although it can be argued that the Doctor stole his TARDIS from a fleet of obsolete models, which is why it looks different in its pre-Police Box form.

As well as the two prequels, this episode appeared in the midst of a series of field reports from Strax, summarizing events in the story and helping to raise excitement over the forthcoming 50th anniversary Doctor Who special, "The Day of the Doctor." These would continue for the rest of the year, including the regeneration special "The Time of the Doctor."

https://www.youtube.com/watch?v=dIz6oyOcD4Q

https://www.youtube.com/watch?v=qYWghABqh3w

NEXT: 10 Things You May Not Know About "The Day of the Doctor"

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