When In Rome...
Parts of the episode were filmed at the world famous Cinecittà Studios in Italy, previously home of the BBC/HBO drama series Rome.
A fire damaged the Rome sets on the day the production team visited the studio for a pre-filming recce, but the blaze didn't affect anything needed for the shoot.
'Praesidium Arca,' the words written on the marble TARDIS at the end of the episode, means 'Committee Box'. Not just any committee though - a committee to a higher power! Also, some of the character names came from the Cambridge Latin course - Caecilius, Metella and Quintus. Except Evelina - they didn't have a daughter, so writer James Moran had to add her, and pick a suitable name. "Evelina" means "little bird". In the books, the family are killed in the eruption - so he decided to save them!
The Fires Of Vulcan
The word 'volcano' comes from the Roman God Vulcan. Vulcan, the God of Fire, was worshiped every year on a day called Vulcanalia. Ironically, the actual eruption happened the day after Vulcanalia.
Impressionist Phil Cornwell frequently impersonated the Ninth Doctor in satirical BBC Two sketch show Dead Ringers.
Return To Rome
Francesca Fowler was no stranger to the set, having appeared in an episode of Series One of Rome.
"She's from Barcelona," is a reference to Sybil Fawlty's regular apology for clumsy Spanish waiter Manuel in classic sitcom Fawlty Towers, not the alien planet the Doctor was going to take Rose at the end of 2005's The Parting Of The Ways.
The magma-based Pyroviles are the second lava creatures to feature in Doctor Who. Sort of. Back in 1979, Douglas Adams created the Krargs for the Fourth Doctor story Shada. Sadly, due to a strike, the story was never completed. An online version, starring Paul McGann, was subsequently produced for the Doctor Who website.
The Doctor previously visited ancient Rome in the 1965 adventure The Romans. The First Doctor arrived in AD64, 15 years before Pompeii's destruction, and met Emperor Nero. "I specifically wanted to put it in, just for a fun continuity thing, but also because it works as a joke even if you don't know what the Doctor's referring to," notes writer James Moran.
This is not the first time the Doctor has asked people to deny he was ever at an event. The Fifth Doctor made the same request to the colonists of Frontios in the far, far future (see 1984's Frontios).
Don't Mess With History
It's not the first time he's abandoned a population to it's historical fate, either. In the 1966 story The Massacre of St Bartholomew's Eve, the First Doctor hurriedly left sixteenth century France, leaving thousands to be slaughtered - to the disgust of his companion, Steven.
One of James Moran's favourite stories is 1979's City of Death, so there's a deliberate reference to that - Caecilius buys the TARDIS, thinking it's a piece of modern art. In City of Death, the TARDIS is parked in an art gallery, causing a pair of critics (John Cleese and Eleanor Bron) to discuss its artistic merits.
What's In A Name?
The line "They didn't even have a word for 'volcano'" is true - the Romans had no idea what a volcano was, or what was happening. The earthquake of 62AD that Caecilius mentions really happened - the town had been rebuilt, although there were regular earth tremors leading up to the eruption, but everyone was used to them, and thought it was just the gods rumbling.
The Name Game
The Pyrovile were originally called Pyrovillaxians. Then this was shortened to Pyrovellians. Then Pyrovile...
When a volcano erupts, it pushes a massive column of rock and ash miles into the air - eventually, this collapses and avalanches down the mountain - this is called a pyroclastic cloud.
When Donna is shouting "Don't go to the beach, go to the hills" she's trying to save lives - many people thought they'd be far away and safe on the beach, but it was completely covered by the pyroclastic cloud.
The time frame of the story is compressed for dramatic reasons, but the eruption lasted well over 24 hours. First it was a massive column of ash and pumice several miles high, that rained down and turned day to night - 10 feet of pumice and ash fell during the day, crushing roofs. Then finally there were five pyroclastic cloud surges, which killed everyone who was left - the final cloud hitpeople in the countryside who thought they'd got away.
Ashes To Ashes
The Doctor says 20,000 people died at Pompeii. We can't be sure how correct that figure is, but 20,000 people did live there - and it's thought that at least half of those died.
When the Doctor calls himself Spartacus, it's the first Roman-type name he can think of. Donna then says "So am I," as a joke, referring to the film Spartacus - the scene in which everyone stands up shouting "I'm Spartacus!"
Compiled with the help of James Moran and Peter Ware.
Return Of The Ood
The Doctor first encountered the Ood in 2006's The Impossible Planet/The Satan Pit. In this adventure, they were under the control of the Devil!