"The Parting of the Ways" is a significant story in the newly regenerated Doctor Who on and off-screen, not least because it's the first regeneration moment in a series that has only just returned to the TV. In order to get to this point, we have to discover that the Daleks are capable of all manner of atrocities in order to survive the Time War, that not all of the Doctor's plans work out for the best, and Captain Jack is given the gift of a lifetime (literally), which separates him from his traveling companions.

Here are a few things that you should keep an eye out for, the next time you watch. (The episode is available on iTunes and Amazon.)

When the Daleks try and shoot the Doctor as he leaves the TARDIS shortly after rescuing Rose, their beams are absorbed by the TARDIS force field, and he dismissively says, "Is that it? Useless! Nul points!" That last bit is a common British expression that derives from the Eurovision Song Contest. This is an annual TV competition in which countries across Europe (and some from further afield) enter a song, and then there's a vote to pick a winner. The multilingual nature of the event has often meant that songs which have scored nothing have to face the embarrassment of being told they have no points in a variety of languages. It's the French nul points which has stuck in the British mindset, however.

As the Daleks attack the TARDIS, Rose says it has no defenses. This has been something of a hotly contested point within the reality of the show. There's the Hostile Action Displacement System that triggers a dematerialization in the event that she's attacked (first seen in "The Krotons," last seen in "Cold War"). The Fourth Doctor adventure "The Armageddon Factor" mentions a force field generator that protects it. There's also the "temporal grace" that the Fourth Doctor claims would prevent anyone from discharging a weapon inside. This appears to have been a fib, as confirmed by the Eleventh Doctor to Mels in "Let's Kill Hitler":

Mels: "You said guns didn't work in this place. You said we're in a state of temporal grace."

Doctor: "That was a clever lie, you idiot! Anyone could tell that was a clever lie!"

Jack refers to the guns on the Game Station being loaded with "bastic bullets," which were projectiles capable of penetrating Dalek casings first used in the Sixth Doctor story "Revelation of the Daleks." Of course, with the Emperor Dalek rebuilding his army painstakingly from scratch, their vulnerability to bastic ammunition was no longer a threat, unless focused on their eye stalks.

https://www.youtube.com/watch?v=xEuV_PGG9EU

This isn't the first time the Doctor has decided to build a delta wave transmitter, although it's the first time he tried to weaponize these brainwaves. In the Fifth Doctor story "Kinda," he builds a delta wave augmenter out of his sonic screwdriver to induce a deep sleep in his companion Nyssa. There was a similarly beneficial effect from the singing sky fish in the Eleventh Doctor story "A Christmas Carol." Their singing created soothing delta waves rather than the sort that could end all life on a planet.

Nisha Nayar, who plays the Female Programmer who shares a little gruff romantic moment with her male counterpart ("Am I supposed to say, when this is all over and if we're still alive, maybe we could go for a drink?") is only the second actor to have appeared in both classic and new Who (the first being William Thomas). She had previously appeared as an extra in the Seventh Doctor story "Paradise Towers," appearing as an uncredited member of the Red Kang gang:

Part of the reason Jack was separated from the Doctor and Rose towards the end of this story has to do with the regeneration. Russell T Davies told Doctor Who Magazine that he wanted Rose to be traumatized by the change, and it was felt that Jack, being from the 51st century and a more experienced space traveler, would take it all in his stride, thereby undercutting the drama of the moment.

Christopher Eccleston told the team that he would be leaving the show after the first season, but while this conversation was taking place (and partly to obscure how the Doctor's regeneration would play out if he did decide to leave), Russell T Davies wrote an alternative ending to the story, with similar dialogue, in which the TARDIS scans Rose after she looks into the time vortex, and the display reads "LIFEFORM DYING."

https://www.youtube.com/watch?v=qa3NM9Jhkn0

David Tennant's post-regeneration lines were recorded quite a while after Billie Piper's and without her being in the room. When he says, "So, where was I? Oh, that's right. Barcelona!" he's actually looking at a piece of sticky tape where her eyeline would be.

Whovian pedants should pay close attention to the final credits, as these are the last time the Doctor is referred to as "Doctor Who" in the credits until the Tenth Doctor meets Jackson Lake in "The Next Doctor." It's a minor point, but does address a common misconception among fans that the Doctor is never referred to directly as Doctor Who. In fact, he has been, many times.

"The Parting of the Ways" was followed, for British viewers at least, by a Childen in Need special showing more of the early moments of confusion between Rose and the newly-regenerated Tenth Doctor, a sequence that would appear in shorter form in "The Christmas Invasion." This aside was given the joke name "Pudsey Cutaway" by Russell T Davies, partly a reference to the Children in Need mascot, a bear called Pudsey. The other half of the joke derives from a standalone Doctor Who story "Mission to the Unknown," which appeared in 1965 as a prequel or trailer for "The Dalek Invasion of Earth." This episode is also known as "Dalek Cutaway," as the Doctor does not appear in it.

With its official name left off the title sequence, the Children in Need Special is also known as "Born Again."

10 Things You May Not Know About ‘The Christmas Invasion’

Now read the rest of the 10 Things You May Not Know About Doctor Who archive.