* ActorSharedBackground: Hacker, Sir Humphrey, and Bernard share birth dates (and dates of death where applicable) with the actors who portrayed them.
* HarpoDoesSomethingFunny: Or in this case, as writer Jonathan Lynn reports putting in the margins of scripts, "Paul doesn't have to say this line if he doesn't want to". Paul Eddington, who played Hacker, had an amazing ability to convey the same sense a line was intended to give with an expression. One particularly good example is [[https://www.youtube.com/watch?v=I9NifqJyDMI 1:10 to 1:30 or so in this clip.]]
* HeyItsThatGuy:
** Jim Hacker is also [[Series/TheGoodLife Jerry Leadbetter]].
** The caricatures and TitleDrop in the opening credits were created by Gerald Scarfe, whose style you might recognize from [[TheWall a certain rock & roll album]].
** Recurring character Sir Ian Whitchurch (or Whitworth) was played by John Barron, who played CJ in ''Series/TheFallAndRiseOfReginaldPerrin''.
** Another recurring character, Sir Desmond Glazebrook, is played by Richard Vernon, who is probably better remembered these days as the original [[Radio/TheHitchhikersGuideToTheGalaxy Slartibartfast]].
** The commissioner of the Metropolitan Police is [[Series/DoctorWho Brigadier Lethbridge-Stewart]].
** Sarah Harrison is (depending on your fanbase) either Miss Minchin in ''Literature/ALittlePrincess'' or Ahme from ''{{Film/Help}}''.
** Commander Forrest of Special Branch was played by [[Series/TheGoodies Graeme Garden]].
** In the 2013 series, the Deputy Prime Minister is [[Film/HarryPotter Hagrid]].
* WagTheDirector: Paul Eddington, a firm believer in nuclear disarmament, once convinced the writers to rework the script of a ''Yes, Prime Minister'' episode that he believed was rather too flippant about NuclearWar.
* ThrowItIn: The moment in "The Official Visit" where Bernard's briefcase falls open and lets his files spill out on the station platform was unscripted -- in fact, Derek Fowlds actually said "oh, shit!" when it happened, which somehow made it into the finished episode (probably because it was only just audible over the noise of the trains).
** Not surprising; Derek always said "shit" every time he goofed.
* WrittenInInfirmity: In ''Yes, Prime Minister'' you might notice that in the later episodes especially, Jim Hacker spends much of the show sitting still behind his desk or in his armchair at home. This is because at the time of filming Paul Eddington was in the early stages of the T cell lymphoma that eventually killed him, and the episodes were written to be as comfortable for him to perform as possible.