Having firmly established Donna Noble as the Doctor's new companion with "Partners in Crime," "The Fires of Pompeii" is a chance to show that her impact on the Doctor is as profound as his impact on her. We get to see her marveling at the possibilities of the life he leads, and have an explanation as to why he can speak and be understood by everyone he meets, but also discover that her moral core is strong and entirely inviolable, no matter what extreme circumstances she finds herself in.

She holds the Doctor to a higher standard than he does himself, as he admits at the end, once he's finally done the decent thing and rescued someone. It's a decision that will prove to have long-lasting impact on him, not least on his own future face, but that's another story.

Here are a few things, beyond the first appearances of both Peter Capaldi AND Karen Gillan, that you should keep an eye out for, the next time you watch.

(The episode is available on iTunes and Amazon.)

When James Moran wrote his script, he based the family who buy the TARDIS on characters from the first book of the Cambridge Latin Course, which focused on a banker named Lucius Caecilius Iucundus, his wife Metella, and his son Quintus. He added the daughter Evelina, and changed the name of their soothsayer from Lucius Marcius Memor to Lucius Petrus Dextus, which is a punning reference to his stone right hand in the story. In the Cambridge books, Caecilius's family actually perish at Pompeii, apart from Quintus.

James Moran originally named his monsters Pyrovillaxitrians (from the Greek “pyr”, meaning “fire”), which was gradually shortened to Pyrovillaxians and then Pyrovellians. Russell T Davies went still further, shortening it to Pyroviles.

There's an exchange between the Doctor and Donna in which her "No way!" is met with his "Yes way. Appian Way!" which is a reference to one of Rome's first and most important roads. The Appian Way connected Rome to Brindisi, in southeast Italy. It was described at by Statius as "the queen of the long roads."

The market trader that sells the TARDIS uses the phrase "lovely jubbly" to denote excitement and approval at his ill-gotten gains. It's a term that comes from London market traders (as in, people who work on market stalls, not the stock market) in the 1950s using a marketing slogan for a popular ice lolly, called a Jubbly, as part of their sales patter. To British viewers it is most closely associated with the British TV comedy Only Fools and Horses, in which a charming market stall owner called Del Trotter tries to buy and sell his way to the top.

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

Another British comedy reference comes in the line, "You must excuse my friend, she's from Barcelona." This is a semi-catchphrase from the 1970s sitcom Fawlty Towers, most commonly said by hotel owner Sybil Fawlty to excuse the errors of their Spanish waiter. Someone in the Doctor Who production team clearly had a fondness for the word, as it was one of the last places the Ninth Doctor wanted to visit (albeit a different Barcelona), and one of the first words said by the Tenth, once he'd checked out his new teeth.

While we're on Fawlty Towers, Caecilius's purchase of the TARDIS in the belief that it's a work of modern art is partly a reference to this scene from the Fourth Doctor adventure "City of Death," in which a pair of art critics, played by John Cleese (the Monty Python star who co-wrote Fawlty Towers) and Eleanor Bron assess the artistic worth of its outer shell:

The streets of Pompeii shots were filmed at Cinecittà Studios in Italy, previously home of the BBC/HBO drama series Rome. Production nearly ground to a halt because of a fire at the studio, in which four people were killed, just before the team arrived to commence filming. However, the sets earmarked for Doctor Who had not been damaged, so it was possible for filming to go ahead as planned.

In the marble shrine to the Doctor and Donna at the end of the story, the TARDIS is inscribed with the legend "Praesidium Arca," which means "Protection Area."

The Pyroviles are the second lava creatures to feature in Doctor Who, but the first to make it to the TV screen. Douglas Adams created the Krargs in 1979, as part of the Fourth Doctor story Shada, the production of which was interrupted by a strike, and therefore never finished. There was a later version made, starring Paul McGann, for the Doctor Who website.

When the Doctor claims "that fire" had nothing to do with him, he's referring to events in the First Doctor adventure "The Romans," in which he accidentally sets fire to a map, triggering the Great Fire of Rome in AD64. "I specifically wanted to put it in, just for a fun continuity thing," said James Moran, "but also because it works as a joke even if you don't know what the Doctor's referring to."

There's a similar emotional continuity between the First and Tenth Doctor when Donna takes him to task for not saving the citizens of Pompeii. The First Doctor appalled his companion Steven in "The Massacre of St Bartholomew's Eve," by leaving thousands of sixteenth century Huguenots to die in an infamous wave of mob violence, during the French Wars of Religion.

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