This is the first episode to use colourised footage of black and white material originally filmed in the 1960s.
Matt Smith and Jenna Coleman were told not to swing on the bars during the TARDIS's fall to Trenzalore. He went and did so, anyway.
This story features for the first time on television the Doctor prior to stealing the TARDIS.
This is chronologically the last event in River Song's personal history, taking place after her death in the Library. It's implied she fades from existence at this point. However, Alex Kingston would reprise the role one last time in The Husbands of River Song (2015), which was intended to be her final appearance in the series.
Clara appearing throughout the Doctor's timeline involved a combination of recording on sets with stand-ins representing various incarnations of the Doctor as well as his granddaughter Susan, plus greenscreen work to insert Jenna Coleman into archival footage.