This episode marks Russell T. Davies's return to the show since series' 4 The End of Time: Part Two (2010), which was David Tennant's final episode before returning in The Day of the Doctor (2013).
Sylvia Noble becomes the third companion's mother to slap the Doctor after Rose and Martha's mothers back in 2005 and 2007.
This episode adapts the comic strip "Doctor Who and the Star Beast". This is the second time it's been adapted, as Big Finish Productions also adapted it as an audio drama four years previously, with Tom Baker as The Doctor in Doctor Who: The Comic Strip Adaptations (2019).
A poster advertising a circus lists an 'Info Line Only' telephone number of 07700-900461; this number was shown in both The Stolen Earth (2008) and the 50th Anniversary special The Day of the Doctor (2013); it is the phone number of the TARDIS. Additionally, a list of show times on the same poster shows Sunday, December 24th followed by Monday, December 26th (the days are in correct progression, but the 25th is absent.)
The area where the TARDIS materialises contains the flagship store of Cyberdog, a genuine fashion outlet at Camden's Stables Market. This is possibly included as an easter-egg tribute to the Fourth Doctor's robot dog K-9.