Harriet Jones first appeared in 2005's Aliens of London. She makes a return here after being ousted by the Doctor in 2005's The Christmas Invasion... and she was right - he wasn't there to help this time.
This isn't the first time milkmen have featured in the series - the Third Doctor disguised himself as one to break into Global Chemicals during 1973's The Green Death and a milkman was attacked by a Cheetah Person at the start of 1988's Survival.
Despite their many encounters, the Doctor's only been shot by a Dalek twice before: in 1973's Planet of the Daleks (when a Dalek deliberately disabled the Third Doctor by zapping his legs) and in 1975's Genesis of the Daleks, when, just prior to blowing up the Daleks' incubation room, the Fourth Doctor received a glancing blow to his hand from a Dalek ray.
Michael Brandon is probably best known for his portrayal of tough 80's New York cop Lt. James Dempsey in the 1980s TV show Dempsey and Makepeace.
Kelly Hunter appeared in the BBC's 2005 adaptation of Bleak House alongside Carey Mulligan, who played Sally Sparrow in 2007's terrifying Blink.
New To Who
The characters of Ianto Jones, Gwen Cooper, Luke and the computer Mr Smith all make their Doctor Who debuts in this episode, although they've already starred in their own shows: Ianto and Gwen in Torchwood and Luke and Mr Smith in The Sarah Jane Adventures.
Lost And Found
Among the stolen celestial bodies are The Lost Moon of Poosh (as mentioned in Midnight) and Calufrax Minor. The Fourth Doctor visited Calufrax in 1978's The Pirate Planet.
Blasts From The Past
The Shadow Proclamation was first mentioned in 2005's Rose; the Judoon debuted in 2007's Smith and Jones; and the Medusa Cascade was first referenced in 2007's Last of the Time Lords.
This isn't the first time Bernard Cribbins has faced the Daleks. He starred in the 1960s feature film Daleks: Invasion Earth 2150 AD as policemen Tom Campbell. The film, starring Peter Cushing, was based on the television adventure The Dalek Invasion Of Earth (1964).
My vision is not impaired
This proclamation by a Dalek, unaffected by Wilf's paintball gun, is a reference to another of the Daleks' famous catchphrases "My vision is impaired!" A Dalek was disabled by obstructing its vision in the very first Dalek story in 1963. We're rapidly running out of ways to defeat or get away from them!
Despite being the longest serving of all the companions featured in this episode, this is the first time that actress Elisabeth Sladen, who plays Sarah Jane Smith, has appeared in the show's opening titles.
Paul O'Grady is a huge fan of the show, and when Russell T Davies heard this, he jumped at the chance to give Paul a cameo!
Richard Dawkins, the celebrated ethologist, evolutionary biologist and popular science writer, is married to the Second Romana, actress Lalla Ward.
Davros has been referenced twice since the series restarted in 2005, but never by name. He was referred to in 2005's Dalek as a "man who was king of his own little world"; and in Evolution of The Daleks as the creator "who removed emotion to make them stronger."
On The Move - Part 1
The Daleks tried to move Earth before, in 1964's The Dalek Invasion of Earth. Their attempts to put pilot the planet were thwarted by the pull of the Earth's magnetic core.
On The Move - Part 2
The Time Lords have also moved the Earth - as part of a shady cover-up in 1986's The Trial Of A Time Lord.
The Supreme Dalek's red colour scheme is a nod to the Dalek Controller from the two 1960s Dalek films.