The clumsily-written, heavily homoerotic novel Mr. Garrison wrote when he got fired for being a teacher becoming a bestseller is funnier now thanks to the Fifty Shades books.
The episode also feels more relevant than ever with the rise of alternative remedies online.
In the Season 2 episode "City on the Edge of Forever" (which spoofs Clip Show episodes by twisting events of previous episodes — and even one scene of the episode itself — and ending each clip with at least one character eating ice cream), the last clip shown was the scene from "Cartman's Mom is Still a Dirty Slut" where Cartman's father was revealed, only instead of the father being revealed to be Cartman's mom (who is revealed to be a hermaphrodite), it was instead John Elway of the Denver Broncos. Then came Season 14, where Cartman's biological father was retconned into being a Denver Bronco.
All the times Kyle told Cartman not to call his mom a bitch become funnier once he actually did it himself in "Fun With Veal".
"Follow That Egg" becomes weird to watch after Colorado legalized same-sex marriage in 2013.
In "Korn's Groovy Pirate Ghost Mystery", Cartman expecting and preparing for Christmas as early as during Halloween is played for laughs. These days, in many places around the world, Christmas shopping season and preparations begin even earlier.
Sheila's unhealthy hatred for an animated movie resembles Sean Penn going out of his way to write an angry public letter telling Trey and Matt how angry he is about Team America.
In "The Cissy", Eric's "Erica" alter ego is portrayed to have more knowledge on gender identity and sexuality issues than most adults, to an extent that's pretty unrealistic for a fourth-grader. Stephie's character in "Assigned Male" is more or less exactly like this..... except A). She's actually trans and B). It's not Played for Laughs.
A season 18 episode makes fun of ride-sharing apps such as Uber, in which Timmy's ride-sharing app is claimed to be illegal because it not only takes away customers from hard-working taxi drivers, but because Timmy is handicapped he can use parking spots taxi drivers can not use. The hindsight comes in nearly one year later, where in Portugal taxi drivers are claiming the exact same thing about Uber, and later Cabify, leading to the local government getting involved (sadly there are no Wacky Races involved this time).
Pretty much the whole main plot of Season 3's "Tweek vs. Craig" becomes this after Season 19's "Tweek x Craig". In the former, the two are goaded into fighting each other and Clyde outright says (albeit slightly misguidedly) that they "really hate each other". In the latter, the two start dating to satisfy the town and end up as an Official Couple, with some later official notes even stating that Tweek is one of the only two things Craig actually cares about.
A later episode, "South Park Is Gay", had everyone turn metrosexual, with Craig being the leader of another 4-boy group (with Tweek being one of them), saying they look pretty gay, before commenting "Not as gay as us, though!". Like the above example, this became funnier after Craig and Tweek became an official couple.
In "Raising the Bar", "Mama June" Thompson admits how ashamed she is about her excessive weight after title titular bar is raised. Since the show aired, Mama June had lost over 150 pounds and barely looks like her old self.
The episode's satire included Mama June's daughter, Honey Boo Boo fighting Cartman in a spaghetti wrestling match booked by former First Lady Michelle Obama.
In "Chef's Salty Chocolate Balls", Cartman describes independent movies as being about "gay cowboys eating pudding". 7 years later, Brokeback Mountain fills 2/3rds of that criteria. Parker and Stone even said in an interview "if there's any pudding eating, we will sue".
In "The Passion of the Jew", Mel Gibson is portrayed as a raving lunatic who loves torture. Tapes to his ex-girlfriend Oksana Grigorieva makes this exaggeration even funnier.
"At least it doesn't get all preachy and up its own ass with messages, you know?": Once a burn on South Park's descent into being more political than funny, it can now also be applied to South Park's biggest rival Family Guy as well.
The whole plot of "Cartoon Wars" is kicked off by Family Guy deciding to show the prophet Mohammed uncensored. Then South Park had Mohammed show up in a full-body bear costume and be demanded that he step out of it in the episode "200" and caught controversy because of it.
The entire episode seems to have become a prophecy for the future of World of Warcraft now that a hacker has started killing large groups of people in major cities.
Osama bin Laden being shot in the head by US soldiers on multiple occasions (namely the season five episode "Osama bin Laden Has Farty Pants" and the season 14 episode "It's a Jersey Thing") becomes funnier now that bin Laden's death (and how he died) has become a reality. As a matter of fact, that episode aired on Australian television the day before Bin Laden was reported dead.
The Movie (which depicts Saddam Hussein in Hell and as the Big Bad) was made years before Saddam Hussein's death, interestingly enough.
"Medicinal Fried Chicken" counts as this, since the state of Colorado subsequently voted to allow marijuana for recreational use.
Also fitting this trope is the length Randy and some of the other men go to get the marijuana since it was supposed to be for medicinal use only.
In "Fantastic Easter Special", we hear a news reporter say that "Pope Benedict has stepped down, ushering in a new era of... Pope Bill Donohue" (since Bill is an American of Irish descent). Nearly six years later, Benedict did indeed step down, and now we have a new American pope (a South American one, if you want to be pedantic, but it still works).
Although this can be applied to many adults of the late 90s, "Chinpokomon" seemed to imply that, like many other "fads", Pokémon would eventually fade into obscurity. Nope, the Pokemon series is still as popular now as it was back then, with Pokemon as a whole being Nintendo's second biggest Cash Cow Franchise (just after Mario), and the anime series actually rivals South Parkin terms of longevity (both premiered in 1997 and are still going strong). Even better, statistics and sales data show that Pokemon is just as popular with adults today as it is with children. Granted most of those adults are probably people who got into the series as kids in the 90s, but it shows that there are adults out there who do understand Pokemon's wide appeal, unlike the adults in South Park.
YMMV on "hilarious", but Mr. Garrison being told that "most teachers don't carry a gun!", demonstrating what a Cloudcuckoolander he is. As of 2013, some groups are pushing for teachers to be given guns in the wake of school shooting tragedies.
The Black Friday trilogy's primary conflict was X-Box One vs Playstation 4. It thought that the X-Box One would 'win' the Console Cycle...but now months later its sales are tanking with Playstation 4's flying off the shelves. It was true even in the holiday season!
The Movie was a fully-blown Disneyesque musical. Years later, we get "Elementary School Musical", which focuses entirely on how the boys react badly to everyone else in the school singing and dancing like the characters in a Disney musical.
Timmy is jealous of Jimmy stealing all of the attention and taking his place as the new crippled kid. This becomes hilarious when Jimmy appears more frequently and actually does end up replacing Timmy in following episodes, with Timmy being Demoted to Extra as a result.
It helps Jimmy that he is able to speak more than one word which helps to explain Timmy's demotion.
Big Gay Al tells the crowd that the law shouldn't force the Scouts to accept gay leaders and instead the correct approach is educate the organization so they will change their mind. In 2015, Boy Scouts of America decided to change their policy without any lawsuits making them.
The opening narration sounds just like the opening narration for Arrow.
Cartman tries to guess Mysterion's identity. One of his guesses is Craig, with the comment that "Only you would think of a name that dumb". Come South Park: The Fractured but Whole, and Craig's superhero name is the decidedly uncreative Super Craig.
In 1997, South Park did a bumper commercial for Magic The Gathering, where Kenny said that it sounded "fucking gay". But fast forward to 2014 and the episode "Cock Magic" involves Magic The Gathering... and Kenny turns out to be a pro at it! Kinda makes Kenny sound like a hypocrite.
In "Eek, A Penis!", Cartman encouraged the inner-city kids to cheat by saying that the New England Patriots cheated all the time. In 2015, the Patriots get accused of deflating footballs. Then in 2017, it is believed that the officials are on their side meaning that the team's opponents have to defeat not only the Patriots, but the refs as well.
In "Fat Camp" Kenny starts eating and doing gross things for money with people egging him to do it and taking pleasure in watching him. This episode premiered 6 months before the premiere of Fear Factor. For an added bonus, Kenny was offered $50,000 dollars for one of his stunts (which got wagered down to $10); $50,000 is the prize money for winning Fear Factor.
The 2002 episode "Jared Has Aides" had Jared the Subway guy falling from grace because he wanted everyone to have aides. Thirteen years later, the real Jared is going to jail for child porn. YMMV on whether it's hilarious or harsh, but it'll probably be funny in 22.3 years.
In the earlier seasons, Mr. Garrison would usually ask during town meetings to Mayor McDaniels to get rid of all the Mexicans. In Season 19, one of Garrison's presidential aims is to literally fuck every single illegal immigrant to death.
In "Dead Celebrities", Kyle questions why people would still eat at Chipotle if they knew it would make them crap blood. This is funnier knowing that Chipotle had outbreaks of e.coli and the norovirus, and this hasn't stopped certain people from eating at Chipotle.
YMMV on hilarious, but in the 2007 episode "Guitar Queer-O", Randy criticizes Guitar Hero because the guitar controls are plastic and that playing a real guitar is cooler, Stan telling him off on it. This is the exact reason the series eventually died in 2010, with Warriors of Rock selling poorly, implying people got sick of band games and found plastic guitars inconvenient. And with the rise of Rocksmith, more people got the kick out of playing real guitars.
In the same episode, Brian Boitano appears in the titular Big Gay Boat Ride. He wouldn't come out of the closet until 2013.
"Chickenlover" was about a perverted criminal having sex with chickens. Cut to 2016, and a guy in real life films a controversial video of him having sex with a McDonald's McChicken sandwich (the incident went viral and the video was deemed disturbing by numerous people).
The Imaginationland trilogy heavily used a lot of nostalgic, fictional characters. In season 20, the punchline with the Member Berries is Hollywood's reliance on nostalgia.
In the season 3 episode "Cat Orgy", after Cartman takes a photo of Shelly with her boyfriend to tell his mom about (since she, according to Cartman, didn't want any babysitter to bring over her boyfriend), Shelly says she'll make a "turd sandwich" out of Cartman if he tells his mom. Cut to five seasons later, Cartman creates a mascot named Turd Sandwich in "Douche and Turd".
The Member Berries get this again with the release of Despicable Me 3, where Trey Parker does the voice of the Big Bad, who is a former child star obsessed with The 80s.
The episode "Freemium Isn't Free deals with exploitative free-to-play games. Years later, South Park: Phone Destroyer was released, itself a F2P game that isn't all that different business-wise from the games that episode was mocking.
Mr Garrison started morphing into the show's Donald Trump parody slightly before pro-Trump political cartoonist Ben Garrison came to prominence.
In "Chef Goes Nanners," the topic is censorship and there is a debate on changing the town's flag which features four white guys hanging a black guy. In his proposal, Chef mentions the Cleveland Indians changing their logo and nickname. In 2017, the Indians changed their logo because the old one was deemed racist.
Cartman tricking Heidi into eating KFC by convincing her it's a vegan alternative in the style of Beyond Meat becomes this after KFC announced they're making vegetarian chicken.
"The Problem With A Poo": The PC babies getting upset whenever someone mentions Monica Lewinsky siding with the Republicans came out the very same week that Taylor Swift announced she was voting for the Democrats, which upset the radical right-wing Americans who put her on a pedestal based on her Aryan heritage.
Cesar Millan being able to tame Cartman in "Tsst!" makes far more sense considering the fact that his training techniques are now considered animal abuse by other animal experts.
In "Spontaneous Combustion," Cartman insists that Kyle can't be Jesus in their "Stations of the Cross" play. Kyle would later act as a Jesus figure in "Margaritaville," with Cartman as the Judas figure to boot.
In "Where My Country Gone," the Canadians are talking about how they had a presidential candidate that everyone made a joke of at the time, then he got elected (so they all fled to America). By season 20, the election suddenly swings a way the authors didn't plan for, and they have to suddenly redo the episode on short notice, changing much of the plot of season 20 after this. In other words, as far as the writers were concerned, they had a presidential candidate that everyone made a joke of at the time, then he got elected.