The Doctor learning of The Brigadier's death was a tribute to Nicholas Courtney, who passed away on 22 February 2011. The episode also contains scenes in which "everybody was wearing an eyepatch", a reference to the alternate universe Brigadier in Inferno: Episode 3 (1970). Furthermore, Amy says to The Doctor "We'll be in Cairo soon", Cairo being Courtney's place of birth.
Steven Moffat said of the reference, "In a story about The Doctor going to his death, it seemed right and proper to acknowledge one of the greatest losses Doctor Who has endured."
Brigadier Alistair Gordon Lethbridge-Stewart is said to have died in his sleep peacefully at a nursing home. In Battlefield: Part One (1989), The Seventh Doctor stated that this was exactly how his old friend would pass away.
This is the first series finale of the revived series not to be a multi-part episode.
The script called for an Indiana Jones style tunnel for the Headless Monks' chamber, but as that kind of location was not available in Cardiff a set was built instead.The skulls were hand-crafted and required a lot of preparation, so it was one of the first things started for the episode's production.
Amy's confrontation with Madame Kovarian, a scene which shows what she might have been like had she not met The Doctor, was also added into the script later.
Simon Callow: Reprising his role as Charles Dickens from The Unquiet Dead (2005), a Ninth Doctor story. This marks the first time that any character (other than The Doctor, River Song, or hive minded characters such as the Daleks) from series 1-4 has appeared on-screen in an Eleventh Doctor story.
Meredith Vieira: a well known American TV news and talk show host is one of the reporters commenting on the time alteration. She recorded her report of Churchill's return to the Buckingham Senate in front of a green screen while filming a segment for Today (1952)'s "Anchors Abroad" segment covering the wedding of Prince William of Wales to Catherine Princess of Wales.