- The Cast Showoff: That really is Capaldi playing the guitar. Capaldi was the lead guitarist in a punk band in his younger days. All of his guitar playing is real.
- Cast the Expert: This is the first of several episodes in Series 9 and 10 to show the Doctor playing guitar, a character facet introduced due to Peter Capaldi's real-life playing ability.
- Lying Creator: In interviews prior to the start of Series 9 (not to mention Series 8), Capaldi was quoted as saying that there would be no flirting between the Doctor and Clara. Notwithstanding his contradictory remarks in the August 2015 interview with Wil Wheaton (in which he directly said the Doctor and Clara were in an old-fashioned romance), one of the very first things the Doctor does in this episode when he is reunited with Clara ... is flirt with her (something Clara herself flags as out of character, although there are additional moments of this nature later in the season).
- Throw It In!: Michelle Gomez confirmed on Twitter that her tickling a nearby Dalek's bumps when referring to the TARDIS as "the dog's unmentionables" was improvised.
Trivia / Doctor Who S35 E1 "The Magician's Apprentice"