Regarding Blackadder's cunning plan to become king, Baldrick asks if it is as 'cunning as a fox what used to be Professor of Cunning at Oxford University, but has moved on and is now working for the UN at the high commission of International Cunning planning?'. This is building on a line delivered by a previous Blackadder to his Baldrick in Blackadder Goes Forth: Goodbyeee (1989), involving a plan 'as cunning as fox who's just been appointed Professor of Cunning at Oxford University'
Brian Blessed, Elspet Gray and Robert East were originally going to reprise their roles from The Black Adder (1983). The scene would have been Blackadder and Baldrick arriving at Bosworth field and killing Henry Tudor with the time machine, however the scene was later changed to the battle of Waterloo as Blessed was unable to reprise his role of Richard IV.
Although not correct to the period, black extras can be seen in the Robin Hood and Elizabethan scenes. This is because of a long-running joke between comedians Richard Curtis and Lenny Henry who apparently always complains that he could have been the extra instead.
In the film, the time machine materializes in a space battle. In "Blackadder's Christmas Carol", Ebenezer Blackadder is shown by the Spirit of Christmas, a vision of a distant future, where his distant descendant Grand Admiral Blackadder is a successful, if ruthless, official of a Universe-spanning Empire, with Baldrick as a thong-wearing slave.