This special was filmed in October 2019 and aired on 1 January 2021.
When The Doctor is about to tell herself a bedtime story, she is reciting 'Harry Potter and the Philosopher's Stone'.
Rehashes the "Have you had work done? - You can talk!" exchange between The Doctor and Jack Harkness, from Utopia (2007) where Harkness met a regenerated (Tenth) Doctor. In its initial use, the exchange was a bit of a personal jab at John Barrowman for actually having had "work done" to himself at the time, but it is unconfirmed if the same applies here or if it simply serves to establish some sort of a humorous trend for whenever Harkness teams up with a regenerated Doctor.
Jack Robertson is said to be called "the American Mike Ashley". Similar to Robertson, Mike Ashley is a British billionaire entrepreneur known for starting in sporting goods and branching out to buying companies such as department stores.
Also rehashes the "where did that weapon come from" gag, again referring to Jack Harkness, from his appearance in Bad Wolf (2005).