These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Adaptation Displacement: The TV show is much better known than the original novels, and two changes they made — Lewis being younger rather than older than Morse, and Morse's car being a Jaguar rather than a Lancia — were eventually retconned by Dexter into his books.
Funny Moments: When Morse and Lewis are investigating a rave, Leis grabs a random cap and starts bobbing along to the music, until Morse gives him a Death Glare and he stops.
Genius Bonus: Not only is the theme music rhythmically based on the morse code for "Morse", but composer Barrington Pheloung liked to hide the killer's name in the incidental music as well. After this became well-known, he started mixing in red herrings.
Harsher in Hindsight: Towards the end of the final episode, "The Remorseful Day", Inspector Morse dies of a heart attack after solving his last case. Fifteen months after the episode aired, John Thaw, who played Morse, passed away on 21 February 2002 in real life. Also, in fiction, the same fate would later befall another detective, thirteen years after Morse, in the final episode of Poirot.
It Was His Sled: Morse's first name is mentioned exactly once in the novels, in the second-to-last book Death is Now My Neighbour (it's also revealed - in different circumstances - in the TV adaptation of said book), and after building up and dropping hints for a long time. Today it's widely known precisely because it was mysterious for so long. And being used as the title of the prequel series, which is a bit of a giveaway.
Magnificent Bastard: Hugo deVries in 'Masonic Mysteries'. Basically spends the entire episode ten steps ahead of everyone, jerry-rigs Morse's home stereo to play really awful Opera (LOUDLY), sets Morse's house on fire with Morse inside, frames Morse using the Internet (in 1990, when few of the older officers realised this was possible), and delivers some utterly fantastic monologuing and Deadpan Snarkery to boot. The fact that he's being played by Large Ham Supreme Ian McDiarmid is really just gravy at this point.
Memetic Mutation: (Pop culture version) It's now widely joked that Oxford is a deathtrap, especially for academics, thanks to the frequency of murders on the show.
Replacement Scrappy: Grayling Russell tends to be regarded as this toward Max. While she isn't overwhelmingly hated by any means, she's definitely considered the least interesting of the show's three pathologists — though admittedly wasn't helped by just getting four episodes, whereas Max and Laura Hobson went on to get more development in Endeavour and Lewis respectively — and the sudden implication of a possible May-December Romance between her and Morse in "The Secret of Bay 5B" wasn't exactly well-received.