This story has been written by Gareth Roberts whose previous Doctor Who stories were "The Shakespeare Code" and "The Unicorn and the Wasp". As well as co-writing "Planet of the Dead" he also wrote the interactive mini-story, "Attack of the Graske". He has also scripted stories for the 2010 series of The Sarah Jane Adventures – The spin-off series starring Elizabeth Sladen as Sarah Jane Smith.
Gareth Roberts based this story on his 2007 Doctor Who Magazine comic strip "The Lodger", which featured the Tenth Doctor, Rose Tyler and Mickey Smith. Although the broadcasted story is not a straight-forward adaptation of the earlier story (especially as the comic strip was written for different characters) it does contain a number of similarities, principally in showing how The Doctor would fare spending time (in Amy Pond’s words) as a ‘normal bloke’. Whereas the comic strip focused more on a domestic set-up the television story involves ‘something at the top of the stairs’. This is not the first time that a non-televised story has been adapted for the television show. The 2007 Tenth Doctor story "Human Nature/The Family of Blood" being an example.
As well as a comic strip by Gareth Roberts, "The Lodger" is also the title of Alfred Hitchcock's first thriller (aka The Lodger: A Story of the London Fog). It's not the first time a Doctor Who story has had a title already used for a movie. Previous examples include "Underworld", "Black Orchid", and "Voyage of the Damned".
"The Lodger" was recorded as part of the seventh recording block along with "Amy's Choice". Location filming took place in Cardiff in early March 2010. The house in which Craig has his flat is in Westville Road while the location for the football match was Victoria Park. The play area there had previously been used as a location in the 2008 Tenth Doctor story "Silence in the Library/Forest of the Dead".
Apart for the very end The Doctor and Amy Pond never actually meet in this story. This is very rare but not unique for a Doctor Who story. In "Attack of the Graske", The Doctor makes it clear he is continuing to travel with Rose, but we never actually see her onscreen.
This is not the first time that a story, since the show was revived in 2005, that a companion has not had a full part to play. This is similar to the 2008 Donna Noble-lite story "Midnight". Previous similar stories include The Doctor and Rose-lite 2006 story "Love & Monsters" and The Doctor and Martha Jones-lite 2007 story "Blink".
During the head-butting scene when The Doctor performs a psychic link with Craig, the faces of some of the previous incarnations of The Doctor are seen. These include the Ninth Doctor (Christopher Eccleston), the Tenth Doctor (David Tennant), the Eighth Doctor (Paul McGann), the Fourth Doctor (Tom Baker), the Third Doctor (Jon Pertwee), the First Doctor (William Hartnell) and the Second Doctor (Patrick Troughton). The Cybermen, Rose Tyler, an Ood, and a Weeping Angel also are shown. For some unknown reason the Fifth Doctor (Peter Davison), the Sixth Doctor (Colin Baker) and the Seventh Doctor (Sylvester McCoy) do not appear in this montage.
Immediately after this sequence The Doctor is heard telling Craig that he is the eleventh incarnation. This is the first time in the revived show that The Doctor has definitively stated how many incarnations he has had.
The Doctor wears the number 11 jersey when playing a football match. This is not only a reference to him being the Eleventh Doctor but also that this story is the eleventh episode of Season Thirty One (New Series 5).
The football team The Doctor and Craig play for is called the King's Arms. These scenes did not require much rehearsal as Matt Smith has previous experience as a youth footballer, having played for the youth teams of Northampton Town, Nottingham Forest and Leicester City. It has been reported that he excelled at the game and originally wanted to become a professional footballer before an injury prevented him from taking it up as a career so causing him to focus on acting instead.
Despite Matt Smith’s previous football experience writer Gareth Roberts has stated that the football scenes was always going to be carried over from the comic story and he began writing it prior to the casting of Matt Smith.
Another coincidence is the 2010 FIFA World Cup England vs USA football match kicked off just as "The Lodger" finished. The timing has been noted by writer Gareth Roberts as a ‘happy accident’.
The Doctor playing football is the second time he has shown exceptional skill when playing a sport when entering a team at the last minute. In the 1982 story "Black Orchid", the Fifth Doctor plays a cricket match and proves to be equally skilled with both bat and ball.
Look out for the scene in the Craig’s kitchen. On the fridge is a postcard advertising the Van Gogh exhibition at the Musée d'Orsay, which The Doctor, Amy and later Vincent Van Gogh himself visited in the previous story, "Vincent and The Doctor".
Also in The Doctor’s room is a print on the wall which appears to be a variation of a Van Gogh sketch of a wheat harvest from one of the artist’s letters written in August 1884.
Craig is heard to use the Eleventh Doctor's catchphrase ‘Geronimo!’ that he introduced in "The End of Time" and also exclaimed in "The Eleventh Hour" and "The Beast Below".
The Doctor is heard to once again mention that bow ties are cool. As he previously stated in "The Eleventh Hour", "Amy's Choice" and "Vincent and The Doctor".
The Doctor refers himself as ‘the Oncoming Storm’ again. (see the 2005 Ninth Doctor story "Bad Wolf/The Parting of the Ways", the Tenth Doctor stories: "The Girl in the Fireplace" and "The Stolen Earth/Journey's End" and the Eleventh Doctor story "Amy's Choice").
After Craig is poisoned by the wall, The Doctor feeds him tea, with the intention of ‘reversing the enzyme decay’ in Craig’s body.
When in the shower, The Doctor is heard singing Verdi's "La donna è mobile" which The Third Doctor previously sang at the beginning of the 1970 story "Inferno".
This is not the first time The Doctor has showered himself on screen. The Third Doctor is seen taking a shower in the 1970 story "Spearhead From Space".
When The Doctor rushes out of the shower, in fear of Craig's safety, he grabs a toothbrush rather than his Sonic Screwdriver. In a later scene The Doctor is seen with a regular screwdriver and asking where the on switch is!
The Doctor at one point is seen wearing only a blue bath towel. Matt Smith appeared similarly undressed in Secret Diary of a Call Girl, which stars Billie Piper, when he was playing the part of one of her clients.
The Doctor seems to have regained the fondness for cats embraced by his Sixth incarnation and later reverted into a dislike by his Tenth (see "Fear Her"). Over the course of the story he is seen conversing with one about its findings when it had visited the upstairs flat. The real name of the cat that features in this story is called Pearl.
According to The Doctor the spaceship, that is the upstairs flat, is an attempt by someone to build a TARDIS. However, it is too weak to link with a Time Lord but too strong for a human.
The centre of the Faux-TARDIS resembles the actual TARDIS' control room seen in the 1996 film "Doctor Who: The Movie". However, the centre console has large orbs for control devices, a characteristic usually seen in Dalek designs.
Another crack in the universe is once again seen, this time in the wall in Craig's flat.
Rumour was that Amy will remember, or begin to remember, Rory by the end of the story. Although she never remembered him enough to say it, she did find the engagement ring from Rory, that previously featured in "The Hungry Earth/Cold Blood", in the pocket of The Doctor's coat. It uncertain if this will spark memories of Rory or if she will assume that The Doctor intends to propose to her himself.
This story was mistakenly entitled "Reality Check", "A Clinical Finish", "Don't Go Up the Stairs", and "Something at the Top of the Stairs".
In the ‘next time’ trailer, clips from "The Eleventh Hour", "The Beast Below", "Victory of the Daleks", "The Time of Angels/Flesh and Stone", "The Vampires of Venice" and "The Hungry Earth/Cold Blood" were shown.
Following on immediately after this story, on BBC3, was the eleventh chapter of the fifth series of Doctor Who Confidential. Titled "Extra Time" which looked into the making of this story. It was presented by Alex Price.
The first time a storyline has been based on a Doctor Who comic strip.
The first time in the revised series that The Doctor has definitively stated how many incarnations he has had.
The first time The Doctor is seen playing football.