* 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.
* 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, though there isn't evidence of it being true, especially since Ethel only looks fat in comparison to Lucy. Get her alone and she's rather thin. Reportedly, Ethel was supposed to be on the heavier side, but Vivian Vance fought against it, arguing that if Fred calls Ethel a fat old bag when she's ''really'' overweight, the scene would fall flat because you'd feel sorry for her. Whereas when he calls her that when she clearly wasn't fat or ugly, the dissonance of it 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!"
* 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.
* YouLookFamiliar: Elizabeth Patterson first played Mother Willoughby in "The Marriage License," then returned during the second season to play babysitter Mrs. Trumbull.
** Charles Lane also had multiple appearances, usually as a different clerk at a government office or business each time. He played an excellent hard-nosed bureaucrat, and in "Lucy Has a Baby" appeared as an expectant father.
** Mary Jane Croft played a former classmate of Lucy's in "Lucy Is Envious" and a nosy airplane passenger in "Return Home from Europe" before becoming a semi-regular as Connecticut neighbor Betty Ramsey in season 6.
** Frank Nelson played eight different characters, including radio host Freddy Filmore and Connecticut neighbor Ralph Ramsey. He was the "Yyyyyyyyyessssss?" guy.
** Ball's close friend Barbara Pepper appeared in eight episodes, each time as a different character.
** The actor who played the Ricardo's milkman in one New York episode returned to play Bobby the Bellboy in the Hollywood episodes.
** Lucy fails to notice that the man she hired to teach the foursome proper English looks exactly like the guy she sold her furniture to a few months earlier.
** Character Actor Jay Novello played a superstitious boss of Ricky, a timid man who witnessed a murder and is subleasing the Ricardo's apartment, and Mario, a gondolier driver the foursome meet in Italy.
* ValuesDissonance: Being made in TheFifties, it's pretty much a given. Probably most notable is that 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."