* BigLippedAlligatorMoment:
** In "The Art of Pornman", before Kevin attends the porn studio tour, he is stopped by a woman who protests the sale of porn. A man explains that he is gay, and only buys gay porn, and the woman allows him in. Neither character appears in the episode beyond this point.
** The scene in "That Guy Who Liked Pie" where Kevin questions how Allen knows how to work a time machine, almost as if Kevin's life was a TV show written by a lazy writer that lacks the talent to create a plausible narrative structure instead of a series of cheap happenstance scenarios that rely on convenient coincidence instead of proper storytelling technique. This is then followed by a rabid wolverine suddenly materializing and mauling Kevin's foot. After this, Kevin decides never to think about such questions again.
** Percy's subplot in "Treble Charger" involves him wanting to kill Chilliwack because "their music will make a man want to kill them". Apart from that mention, Chilliwack doesn't appear in the episode.
** In "Mont Surreal", Kevin and Percy climb on top of the train they're riding to elude authorities. While they're up there, a man with only one arm runs by and tells the two that "They didn't see nothin'." He never shows up again.
* CreatorsPet: Percy largely became the main focus in the later seasons, especially late in the series run where the episodes practically revolved around him (while Kevin was DemotedToExtra), including plots like Percy getting plastic surgery ("Plastic Percy"), Percy having illegitimate children ("Legitimate Claims"), and Percy getting his dick shredded off by a paper shredder ("Blow Job"). It reached a head in the last season, where the intro was primarily about Percy, with Anastasia and Kevin only being mentioned in a single passing lyric.
-->''Alas, his wife is just a big, fat whore / And his son is rotten to the core...''
* MemeticMutation: [[https://www.youtube.com/watch?v=r-jacbXXSRU "My dad has pictures of your mother naked."]] [[labelnote:Explanation]] In "Dreamland", Kevin dreams he's in a parody of ''Oh That Lewis!'' titled ''Oh That Kevin''. When one kid calls Allen out for swearing, Kevin fires back with this line, causing him to cry. The audio from the scene became popular through [=TikTok=] and VideoGame/GachaLife. [[/labelnote]]
* MoralEventHorizon:
** In "The Cruise", Kevin kills the man who nursed him back to life because he stepped on his hat.
** Percy crosses it in "Invisible Sociopath" by selling Kevin to the Quebec mafia to get a reward for turning in the man who slept with one of the members' wives.
** Shawna crosses it at the end of her debut episode ("Jacked In"), where she turns off the virtual reality machine while Kevin and Percy are still inside, which damages their brains.
* TheyCopiedItSoItSucks: Some have compared its writing and animation to ''WesternAnimation/SouthPark''. Notably, Greg Lawrence stated in a 2003 news interview about how proud he was of the show and how he thought it would be the next ''South Park''.
* TooBleakStoppedCaring: The show takes place in a borderline CrapsackWorld where our protagonist is a sociopath who regularly breaks the law just because, looks out only for himself most of the time, and is able to manipulate people into thinking he's on their side when he wants something from them, his parents frequently abuse each other or get into fights over minor inconveniences, and the supporting cast is either just as cold and/or idiotic as the main characters, and what few nice characters there are tend to get shrugged off.
* UnintentionalPeriodPiece:
** The technology used shows its age: The Spencers are so poor that they own a CRT TV with an antenna connection, most computers are the "boxy" type, and most of the phones featured in the series are the rotary-dial type. The crew seemed to catch on with this, as in the later episodes, the Spencers own a cordless wall phone.
** "The Stripper Strikes Back" features Percy attempting to put a stop to a liquor strike by calling every single person involved and explicitly saying his name to them, causing him to be attacked by every last one of his victims at the end of the episode. Such a plot would be laughable today, as Percy (and by extension, his victims) are shown with rotary-dial phones; with modern smartphones having caller [=ID=] and location tracking, Percy would be caught and tracked down far more easily nowadays.
** "Jacked In" depicts Kevin being addicted to an arcade game (therefore meeting Shawna in the process), and the opening sequence depicts Percy playing various machines, dating an episode to a time when arcade machines began to decline in popularity outside of Japan. Furthermore, Kevin and Shawna's virtual reality fight is clearly a reference to ''Film/TheMatrix''.
** The "Bruno Gerussi Must Die" duology feature a multitude of dated pop-culture references, with parodies such as "[[Series/DegrassiJuniorHigh Degrassi Jr.]] Franchise/PowerRangers", "Degrassi [[Series/DawsonsCreek Creek]]", "Series/{{Survivor}} XII: Northern Manitoba", and "Bruno Gerussi Must Die Again" opens with Kevin getting Percy on "[[Series/WhoWantsToBeAMillionaire Who Wants to Marry a Prostitute?]]".
** The guest stars also date the series. "Buzz" features Daryn Jones and Morgan Smith, the hosts of ''Buzz'', a sketch series which aired on The Comedy Network, and the episodes "Spankdriven" and "Treble Charger" have appearances by the namesake bands voicing themselves, with Music/Sum41 also appearing as themselves in the Treble Charger episode. ''Buzz'' would end in 2005, and the bands (with the exception of Sum 41) would fall to obscurity afterwards, with Treble Charger disbanding in 2006, a year after ''Kevin'' ended, and wouldn't reform until 2012, well after ''Kevin'' ended.
** "The Buck Stops Here" could have only been written in 2004, as it features a scene in which Percy goes into a rant against then President George W. Bush.
* ValuesDissonance: The rampant politically incorrect humor would not fly in a television series nowadays, the most blatant example being the outright homophobia through the frequent use of "fruity", itself a homophobic slur. Scenes such as Percy telling Kevin "bible says homos is wrong" in the first episode as well as Percy fearing that Kevin will become fruity from reading a book in "Keep the Home Fires Burning" come off as a lot less funny nowadays, especially as Canada became more accepting of the LGBT community after the series ended. The show outright lampshaded this in "Beach Blanket Bloodbath" where a gay character refers to himself as an offensively gay stereotype.
* ViewerNameConfusion: Some subtitles for the show on streaming services refer to Allen as "All'''a'''n". The season six intro also refers to him as such.
** Similarly, Shawna's name is sometimes written as "Sha'''u'''na" by both fans and subtitles on streaming services. "Mother's Little Helper" confirms that it's actually spelled "Sha'''w'''na".
* ViewerSpeciesConfusion: Allen is a goose, but his design resembles a duck, largely due to him being yellow, a skin color which real geese don't have. Lampshaded in "Dreamland" where a kid from Kevin's "Oh That Kevin!" dream calls him a duck, and his character bio from the official website, which Allen explicitly tells readers that he is not "a fucking duck".