* EarWorm: "It's all right, it's okay"
* HeyItsThatGuy: [[Creator/SharonSmall Barbara]] [[Series/InspectorLynley Havers]] appears in "Queen and Country". Susan Jameson appears as a rich and attractive girl in ''UFO''.
* HilariousInHindsight: In one early episode Gerry is told by a scrap metal merchant that his car, a classic Triumph Stag, is barely even worth scrap metal prices because no one buys them. The joke obviously being on Gerry, since he is only there on enquiries about the case, for driving a rubbish car. Since that episode was made, classic car prices have sky-rocketed and Triumph Stags have become retro-cool with even bad examples making serious money (this is partly due to the discovery that the "problems" Stag engines had was actually due to their radiators not being flushed properly by owners as part of the maintenance regime).
* ItWillNeverCatchOn: TV critic AA Gill has been widely mocked for claiming the show would sink without trace when it first debuted; of course it has not only been going for more than a decade with very high viewing figures, but is also one of the most popular British export programmes.
* MagnificentBastard: MI5 agent Stephen Fisher (played by Tim [=McInnerny=]) in Series 9.
* PlayingAgainstType: Several examples over the years.
** Tim [=McInnerny=], known for playing foppish or pathetic characters on ''Series/{{Blackadder}}'' and an inept villain on ''Series/DoctorWho'', played the sinister MagnificentBastard MI5 agent Stephen Fisher in Series 9.
** [[spoiler:Richard Briers]], known for playing the pleasant [[spoiler:Tom Good in ''Series/TheGoodLife'']], played a villain in "Old Dogs".
* SuspiciouslySimilarSubstitute: Averted with Steve replacing Jack, as they are very different characters. Less averted for Dan replacing Brian, as they are both TheSpock and have family issues (though different ones) and for Sasha replacing Sandra.
* TheyChangedItNowItSucks: The reason Waterman is leaving the show - with the departure of all of the other members of the original cast Waterman has gone on record to say that he misses the chemistry he had with them and it's just not the same without them so he's decided to move on too.