* AndYouThoughtItWouldFail: CBS initially responded to Lucille Ball's insistence that Desi Arnaz play the husband in her TV show by saying they weren't sure if audiences could believe that a celebrity like Lucy was married to an obscure Cuban bandleader. In response, Lucy and Desi gave a vaudeville tour across the country. The tour became a success, proving to the networks that a TV show of the duo would be huge.
* BetterOnDVD: For years, syndicated reruns would edit the episodes for time, and would lack the animated sponsor messages and bumpers. The DVD and Blu-ray releases restore every episode to their original running time (which, back in the '50s, would often mean 26 minutes per episode, virtually unheard of today) and included the animated bits.
* BrokenBase: CBS aired colorized versions of the ChristmasEpisode and "Lucy's Italian Movie" in December 2013. This didn't mark the first attempt to colorize ''I Love Lucy'', but it did prove divisive among viewers: Some liked the fact that the picture looked more natural than that of an early-'90s colorized print of the Christmas episode, and felt the color added to the humor. Others disliked the fact that the picture still looked less natural than the original monochromatic versions, and couldn't stand the mere thought of altering the picture in so drastic a fashion. In any case, the ratings proved high enough for CBS to make an annual tradition -- and later, ''bi''-annual tradition -- out of colorizing ''I Love Lucy'' episodes, and eventually apply similar updates to other black-and-white sitcoms in their library.
* FunnyAneurysmMoment: Any episode that involves a joke about philandering, or Lucy and Ricky's marriage being in trouble, [[MistakenForCheating or both]].
* HarsherInHindsight: Watching the episodes 'Lucy Meets Charles Boyer' and 'Lucy and Superman' are particularly saddening, knowing both Boyer and Reeves ended their own lives.
** From 1951-1954, Phillip Morris cigarettes was the show's only sponsor. Desi Arnaz died of lung cancer at only 69.
** Watching all the tender moments that Lucy and Ricky shared together can be hard to watch when you learn that Lucille Ball's real life marriage to Desi Arnaz ended in divorce literally the day after filming wrapped on the final episode of ''The Series/LucyDesiComedyHour''.
* HollywoodHomely: Ethel, and to a lesser extent Lucy. While both were never referred to as ugly, many times there would be a reference to how unattractive the two are (especially Lucy) when put next to the younger, fancier Marlyin Monroe-esque types that occasionally appeared in Ricky's shows. This is ironic as both Lucille Ball and Vivian Vance began their careers as models and showgirls.
* HollywoodPudgy: UrbanLegend has it that Vivian Vance (Ethel) was contractually obligated to remain overweight, which was born out of a mock contract that Lucy presented to Vivian strictly as a joke, and which Vivian later read for laughs on ''The Dinah Shore Show''. Ethel's stockier appearance was obtained by dressing Vivian in unflattering costumes and too-small undergarments, not by intentional weight gain on Vance's part (at her insistence, the character's wardrobe and style would become more flattering as the series progressed). Vivian fought against Ethel being too heavy, arguing that if Fred called her a fat old bag if she were ''really'' overweight, the scene would fall flat because you'd feel sorry for her; whereas if he called her that when she clearly wasn't fat or ugly, the dissonance of it would instead makes it funny.
** From ''The Young Fans'' episode: "Keep jiggling, Peggy."
** "Are you tired, run down, listless? Do you pop out at parties? Are you unpoopular? The answer to all your problems is in this little bottle!"
* RetroactiveRecognition: Actors who appeared on this show early in their careers include Richard Crenna, Bart Braverman and Barbara Eden.
* SeinfeldIsUnfunny: This show ''invented'' the modern sitcom, and every single sitcom that has ever existed since has borrowed something from the lexicon it created, to the point where things that were groundbreaking in the '50s are not even noticable, let alone edgy... unless you are blocked by the NostalgiaFilter. And somewhat ironic for this trope, both the real and sitcom versions of Jerry Seinfeld have proudly noted having NEVER watched an episode of "I Love Lucy" in their lives.
* ValuesDissonance: Being made in TheFifties, it's pretty much a given.
** Having (white) people play "Indians" in Ricky's show comes up fairly frequently. While more than acceptable in the time us was filmed in, it's known to be an extremely offensive practice today.
** Much like ''Series/TheHoneymooners'', Ricky would occasionally make an empty threat to hit Lucy, which would never be seen today even at that level. Desi Arnaz actually mocked this himself when he hosted an episode of ''Series/SaturdayNightLive'' and presented a series of "failed concepts" for the show, including one where Ricky was openly physically abusive called "I Loathe Lucy."