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.
Norm has admitted to Sam and Diane he's lying about neglecting his wife. Any time his marriage is threatened, Norm becomes desperate to keep it together. It's also hinted that Vera is quite beautiful.
Not to mention the dangerously paranoid, delusional, sexually dysfunctional and possibly matricidal postal worker Cliff Clavin, who stalks TV personalities, writes threatening letters to politicians and has an unhealthy obsession with conspiracy theories and government plots. Hell, even WITH the laugh track the character is slightly uncomfortable to watch at times.
Character Derailment: After Diane left, all traces of Sam's problems vanished. His alcoholism became a non-issue, his womanizing was more of a joke than when Diane was zinging him for it, and even Word of God pointed out (after the show had ended) that following the change from the Diane era to the Rebecca era, the series began to depend less on clever writing and more on physical humor. This was pointed out in the documentaries in the DVD releases.
Dude, Not Funny!: "Simon Says", the episode famous for guest-starring John Cleese as Dr. Simon Finch-Royce—a couple's therapist who's supposedly famous for being able to solve any marriage problem—derives much of its humor from his early insistence that Sam and Diane are not only a mismatch, but "You two should never see each other again!" Diane is eventually driven to tears by his obstinate refusal to even consider her arguments to the contrary. In addition, it's implied the man isn't really doing his job, here—he just wanted an easy $1500 from Frasier, who'd hired him as an early wedding gift to Sam and Diane. (He even brags about having just extorted Frasier of said money, over the phone.) Remove the laughter of the Studio Audience, and you have a pretty dark story of a contemptible character who basically puts undue mental pressure on our couple out of sheer laziness and greed.
Two notable instances of Studio Audience laughter arguably intruding on an otherwise powerful sequence: a couple moments in the Tear Jerker climax of Season One's "Let Me Count The Ways", and (as noted by this Cheers blog/tumblr) during Sam's more caustic barbs in Season Five's "Knights Of The Scimitar" (again, Diane's near tears at at least one point).
Al, played by Al Rosen. He first appeared exclaiming "Sinatra!" in one episode, and was such a hit with the writers, he was given more and more punchlines by the writers. He was later referenced in Frasier episode Cheerful Goodbyes when Cliff told Phil, "You've always been there for me, Al", and Phil retorted, "I'm Phil. Al's been dead for fourteen years, you dumb son of a bitch!"
Fridge Brilliance: Dr. Simon Finch-Royce (John Cleese) of "Simon Says" is a famous marriage counselor. After describing his reputation for successful curing of marriage problems, Diane notes that rumor has it he even counseled Prince Charles and Princess Diana. Uh-huh. Considering what happened between that famous couple, soon after...in hindsight, this can easily be seen as something of an accidental indication that maybe Diane, after hearing his "advice", is on to something—Dr. Finch-Royce really is highly overrated.
Fridge Horror: Closer to Fridge Sadness. In the first part of the tenth season, Sam and Rebecca have a character arc in which they attempt to have a baby. (This was an attempt to incorporate Kirstie Alley's pregnancy into the show.) The arc ends when Sam and Rebecca realize they're not ready to be parents and Sam imagines the son that will never be fading away. It's rather sad on its own, but it gets sadder when you remember the real reason the arc was abandoned: Alley had miscarried.
"Funny Aneurysm" Moment: One episode saw Sam give a radio interview in which he makes disparaging comments of Diane. She gets mad. He gets apologetic. Years later, recurring cast member Jay Thomas gave a radio interview in which he made some disparaging comments about Rhea Perlman. She got mad. He got fired.
Another episode had Cliff taking medication for work-induced stress. He does comment that he has job security and asks rhetorically "What would we do without the U.S. Postal Service?" Woody replies "Probably fax everything and it will get there faster, cheaper, and more efficiently." This just adds more stress to Cliff. Twenty years later, the Postal Service would find itself falling on hard times due to the proliferation of e-mail which delivers messages "faster, cheaper, and more efficiently".
Harsher in Hindsight: Remember the episode when Frasier presented Lilith a prenuptial agreement, and she got pissed off? That scene's a little jarring to watch now, knowing that much later Frasier and Lilith will get a divorce..... because Lilith cheated on Frasier.
Frasier makes his first appearance during the intervention for Sam, who had fallen off the wagon. Becomes a lot harsher in retrospect, as by the end of the series, Kelsey Grammer's own battle with alcoholism and substance abuse forced the cast of Cheers (and later Frasier) to hold similar interventions, though thankfully the latter one stuck.
Hilarious in Hindsight: Right after Frasier is first turned down by Lilith, Sam sets him up with an old girlfriend Candy as a one night stand and Frasier ends up impulsively getting engaged to her, prompting Diane to intervene. Later on in Frasier, the same actress plays another cheap date Frasier plans to spend the night with, only this time it's interrupted by the woman he loves walking in.
In one episode, Diane keeps pronouncing "mime" as "meme", saying, "Everybody loves a meme!"
In Season Five's "Abnormal Psychology", Norm and Cliff return from a "gladiator film festival" arguing about the number of anachronisms in what they've seen. Their exchange about a taxi cab allegedly being in one of the films can easily cause viewers today to instantly think of the 1999 movie Titus (famous for its use of motorcycles and cars in Imperial Rome)...though the episode first aired thirteen years before the movie's release!
Hollywood Homely: In an early episode, Carla's son Gino is mentioned as looking "goofy," with Sam being equal parts amused and insulted that Carla chose him out of all her kids to be Sam's supposed son in a prank she was pulling on Diane. When we actually see Gino much later in the show's run, he looks completely normal. Possibly justified by the time span involved, and Gino just growing up to be much better-looking than when he was a kid.
Les Yay: Diane and Carla. In "Father Knows Last", when they're caught in a most awkward situation.
Mary Sue: Sam's brother Derek, a successful (and supposedly handsome) lawyer, who stops by the bar at the end of the first season spends the entire episode offscreen in the backroom wowing the regulars with his singing, piano playing, tap dancing and pool tricks. Over the course of the night he gets the unemployed Norm a job at a high end accounting firm, teach Coach fluent Spanish, seduce Diane into going away with him on his private jet and have all the customers fight over who should get the pleasure of buying him a beer. All while Sam stands alone at the counter in the front room having to hear from anybody who steps in how terrific his brother is. Sheesh, no wonder he has an inferiority complex.
Diane: Oh Sam, he's not that great. The man can tell an interesting story, he's met a few interesting people, but he's just a man, like any other man you'd meet in Greek mythology.
On the other hand, no one benefited from Derek, like Norm, in the end. When Derek leaves, the bar expresses disappointment. Derek may have talents, but Sam has friends.
Never Live It Down: Zig-zagged for Sam. People like to throw Sam's previous alcoholism in his face as a low-blow, in particular how it ruined his lifelong dream of pitching in the Major Leagues, but others (including Diane) are very impressed that Sam was able to kick the habit and get his life together. It takes a lot of willpower to not drink when you work in a bar.
Played straight for Diane. The constant gags Season 3 on, about someone or something happening to remind us of her time at Goldenbrook. These moments invariably have poor Diane insisting that it wasn't nearly as bad as everyone says....
Season 4 on, Frasier persists in reminding her (and everyone else) about her breaking his heart. And he's not the only one...
It's even worse when you consider how this plagues her even when she's off the show (if Frasier's lines about her during the Rebecca years are any indication)—all the way up to when she comes Back for the Finale...and even in her special appearance in Frasier.
Rescued from the Scrappy Heap: Rebecca often tread the line of almost falling into Replacement Scrappy, especially for fans of Diane. (Despite the fact that the writers strove to make her different from Diane from the beginning, the character still suffered a LOT of unfavorable compare/contrasts with her predecessor from fans of the old days, a la "Diane would've never done that!" Especially when letting Robin walk all over her while seeming oblivious to his manipulations of the rest of the gang....) Once the writers switched her from half-Ice Queen/half-hopeless-piner-for-rich-guys to the cutely neurotic mess she was for the rest of the run, fan animosity cooled.
Frasier was disliked during his early appearances (Kelsey Grammer even received hate mail). Obviously, things got better.
Lisa Kudrow appears as a community theater actress in the episode Two Girls for Every Boyd.
JimNorton appeared as the brother-in-law of Cliff's co-worker Twitch, who conned him into thinking Pimp Duds were the new official postal uniform.
Carmen Argenziano is the furious husband who tries to shoot Sam for sleeping with his wife.
Shipping Bed Death: Apparently, the show creators decided to break up Sam and Diane at the end of Season 2 because they were afraid this was starting to happen. Actually lampshaded by Diane herself in that Season's "Coachie Makes Three", when she openly worries if she and Sam are starting to become "routine".
Super Couple: The "Sam & Diane" pairing is one of the most influential and well-known on-screen romances in the history of American television.
They Wasted a Perfectly Good Plot: Many fans often express their dissatisfaction with much of the first half of Season 5, regarding how it handles the Sam/Diane relationship. Though Diane as The Pollyanna (driving Sam nuts in the process) is admittedly cute, these fans argue it gets old pretty fast. The dramatic implications of the dynamic (including the implication that Diane's being a Type-A Stepford Smiler, clinging on to her hope that Sam will propose again because she doesn't think she'll be able to deal with the alternative) are explored quite wonderfully in the Season's second episode, "The Cape Cad"—and it's picked up again a while later in the excellent "Knights Of The Scimitar". Everything in between may have its moments...still, when taken as a whole, it seems very much like mere "filler"—and could easily be interpreted as the writers stalling for time before settling on whether or not they should bite the bullet and put the show's Super Couple on the path to marriage.
The worst part? Shelley Long would later strongly imply that the writers' constantly putting off answering the question (posed by her and by Ted) of "When will Sam & Diane marry?"...was a major factor in her decision to leave the show.
Values Dissonance: Probably the record for shortest time interval between the example and the values shift: Rebecca's dilemma with her spring-chicken boss's unwelcome advances was only three years before the Clarence Thomas confirmation hearings made sexual harassment a major workplace concern all over the country.
Though we may have been on Sam's side in Season 5, when he expresses his frustration over Diane turning down his proposal in the season premier, her teary-eyed reaction to his pledge to never propose to her again is enough to turn even the hardest of hearts. Including Sam.
Another particularly dramatic example is in "Strange Bedfellows, Part II", when poor Diane is forced to bear witness to Janet making out with Sam (and trying to convince him to fire her).