- Acting for Two: James Callis, playing twins of very different character.
- Actor Allusion:
Lady Annabel: I suppose you want to know how I killed Freddy.Barnaby: But Sir Freddy died from natural causes.Lady Annabel: Oh... of course.
- In "Picture of Innocence", Liza Goddard guest stars as a character who partly drives the plot, but only actually appears in the last couple of minutes of the episode. She's someone who Tom Barnaby says he used to date, briefly, about 30 years ago. In The '80s, Liza Goddard had a recurring role opposite John Nettles in Bergerac as someone who had a flirtatious relationship with Jim Bergerac.
- In "The Axeman Cometh", Michael Angelis plays the drummer in blues rock band Hired Gun. In one scene, the band's singer (Suzi Quatro) scathingly calls him Ringo. Angelis took over as the narrator of Thomas the Tank Engine from Ringo Starr, as they have very similar voices. Also, Michael Angelis' brother Paul provided the voice for Ringo in Yellow Submarine.
- In "Vixen's Run", the plot kicks off when elderly Sir Freddy Butler dies at dinner. Despite there being traces of strychnine in his system, the coroner rules natural causes as strychnine is an ingredient in heart medication and Sir Freddy was rather old, fat and drunk. Several other members of his family are killed over the course of the episode by Sir Freddy's first wife Lady Annabel, played by Sian Philips. When she's taken away by Barnaby in the police car at the end she says:
- Casting Gag: In "The Magician's Nephew", which shares its title with the C. S. Lewis book of the same name one character is played by Ronald Pickup, who had voiced Aslan in the BBC adaptation of The Chronicles of Narnia.
- Cowboy BeBop at His Computer: Midsomer is a county, not one village, contrary to what TV announcers and others will tell you. The fact that there's an actual English village called Midsomer Norton really doesn't help. The "deadliest village in Britain" tag could be applied to Badger's Drift, a very common locale where (judging by rough guess) everyone in the town has died or been a murderer, but that's not generally how it's used.
- The Danza: Hugh "Lord Grantham" Bonneville, playing Hugh Barton in "Ring Out Your Dead".
- Fake American
- Germans Love David Hasselhoff: Midsomer Murders is very popular in Denmark under the title Barnaby. The joke goes that since Barnaby started, Danes who visit idyllic English villages tend to get uneasy and paranoid - and if they see a fair or a wedding in progress, they get out of town as quickly as possible.
- This also resulted in the 100th episode being centered around a killing in Copenhagen, Denmark.
- Hey, It's That Sound!: One of the "something bad is happening/about to happen" sounds is the same as the Temple of the Damned from Warcraft III.
- You Look Familiar:
- The actor who plays John Barnaby first appeared on the series a decade earlier as a murder suspect, a sleazy gardener who hits on Barnaby's wife.
- Guest stars from previous episodes turn up from time to time in different roles, which can be amusing if they got killed during their earlier appearance. This makes Dead Letters stand out all the more for having Barnaby actually react to this (the returning actors turns out to be playing sister and cousin, respectively, of their previous roles).
Trivia / Midsomer Murders