Hilarious in Hindsight/Comedy

Yes, Comedy is supposed to be funny by its nature, but sometimes, in hindsight it becomes even funnier.

"Stephen Colbert: "Hoo-hoo-hoo...it's funny because I'm about to kill him.""
 * This article in The Onion predates the popularity of five-blade razors by some time.
 * And earlier, Saturday Night Live had a gag ad about three-blade razors. "Because you'll buy anything." Now, if only three-blade razors actually fit in Trac II handles...
 * And a Weinerville skit was for a six-blade razor. Impossible, you might ask? I give you the Gillette Fusion, a five-blade razor with an added "precision trimmer" blade on the back of the head.
 * One skit on The Onion News Network had a representative of Al-Qaeda get into a furious argument with a 9-11 conspiracy theorist who claimed Al-Qaeda did not plan and execute the 9-11 attacks. The Al-Qaeda represenative assured the conspiracy theorist that Al-Qaeda was, in fact, responsible. Later, the real Al-Qaeda representative, al-Zawahiri, released a statement attacking 9-11 conspiracy theorists and claiming 9-11 conspiracy theories were all a plot by Shiites to discredit Sunni terrorists, as shown in this article.
 * This Daily Show interview with Liam Neeson, and the strange course it quickly takes, converted this recent Onion skit from pointed satire to simple parody. Conspiracy may be at work.
 * One Onion article, Progressive Parents Refuse To Tell Child Its Sex, got a lot funnier when a couple who kept their child's gender under wraps made headlines.
 * In the Sports section, there's "Brady Quinn: 'I'm Going to Be a Bust'"; which is funny for three reasons:
 * Brady Quinn has been a bust so far, largely sitting on the bench for much of his career.
 * One of the players he suggests people look at in his place is JaMarcus Russell, who would go on to make a solid case for "biggest draft bust of all time".
 * The article mentions that Al Davis was more interested than ever in drafting him. Davis would draft the aforementioned Russell.
 * Traditionally, The Daily Show (and before that Comedy Central in general) calls its coverage of the presidential elections "Indecision (Year)"... as the recounts dragged in the Bush/Gore race, Indecision 2000 just kept getting funnier and funnier.
 * Lampshaded by host Jon Stewart on November 8th - "Calling this whole thing Indecision 2000 was at first a bit of a light-hearted jab, perhaps an attempt at humour - we had no idea that people were gonna run with that. We thought we were kidding, quite frankly."
 * For his column the day after the 2000 election, humorist Dave Barry did an election result analysis, which had lots of blanks and instructions to the editor to fill them in with the winner. The joke was supposed to be that he just watched Buffy the Vampire Slayer instead of election coverage and didn't bother to find out who actually won. The way it actually turned out made it a lot funnier.
 * In a game of "Newsflash" on Whose Line Is It Anyway, Colin started it off by saying "It all started with a badly timed bald joke." The rest really needs to be seen. Also Late to The Punchline: the moment came quite some time later when they were back in their seats, with Colin muttering, in part sportsmanship, part horror, "I said the bald joke thing too."
 * This Letterman sketch seems much funnier to fans of Torchwood...
 * Planet Half-Life once did an April Fools' joke announcing Half Life 2...
 * Similarly, Kryptonsite's annual April Fool's news articles regularly foretell actual developments on Smallville. The introduction of Mr. Mxyzptlk, Pete Ross leaving, and the Lex/Lana relationship were joked about in 2004, Dean Cain appearing on the show was foretold in 2005, 2006 spoke of an episode called (and including) Bizarro, while 2007 suggested an episode called 'Kara' might introduce Supergirl to the show, while 2008's April Fools mentioned an episode called 'Legion'. In some way or another, every one of those has come true...
 * Another example of a strange convergence between real news stories and The Onion is discussed here.
 * There was a sketch in In Living Color with Home Alone and Michael Jackson was made in 1992. Before any of the sequels were made, and before the accusations came out. The dialog makes it even funnier.
 * And there's also the exchange "I've got naked pictures of my sister." "Who doesn't?" Quite true after a certain Wardrobe Malfunction. (At the time, it was a reference to La Toya's Playboy appearance, which makes the gag doubly funny now.)
 * Never Mind the Buzzcocks: When Mark Lamarr introduced guest Simon Amstell, he listed his achievements and joked "He's stealing my act!". Exactly three years later, guess who took over hosting the show...
 * Tim Clague uploaded the short video God Versus The Advertising Standards Authority about a priest being told to edit his "misleading" Christmas advert. Two weeks later, Stephen Green of Christian Voice complained to the ASA about an atheist advert on buses, apparently not realising what impact any such ruling would have on Christian adverts.
 * In 1994, Saturday Night Live puts on a sketch involving "Steve Martin's Penis Beauty Cream", featuring the line, "Just take a small amount and rub gently on the penis for several minutes up to a half-hour. You'll notice a difference right away!" Everyone laughs. About a decade later, Maxoderm hits the market, with the exact same advertising pitch.
 * Saturday Night Live also accidentally predicted Spike TV in a sketch where fake commercials for "The Man Channel" showed nothing but cars crashing, driving off cliffs, and generally exploding at the slightest provocation in Slo Mo.
 * Then there's this sketch on the season 30 episode hosted by Tom Brady, where Seth Meyers plays Peyton Manning, who asks Tom Brady why Brady was chosen to host over Manning. The real Peyton Manning would host two seasons later.
 * The last sketch of the season 34 premiere episode hosted by Olympic swimmer Michael Phelps had a fake commercial for Michael Phelps' infamous 12,000-calorie diet that only works for him (and a cameo by Subway spokesman, Jared Fogle, who declares that the Michael Phelps' Diet "sucks a foot long"). Fast forward to the Bradley Cooper/TV On the Radio episode on February 7, 2009, where Seth Meyers does a Weekend Update joke about Michael Phelps getting busted for smoking marijuana from a bong, with the punchline, "Though, suddenly, the Michael Phelps Diet makes a lot more sense," with a photo of Michael Phelps surrounded by two stacks of pancakes (which were featured in the "Michael Phelps Diet" commercial). Fast forward further to June/July, where Subway actually had a commercial with Jared Fogle and Michael Phelps, together again. It's like a real-life Chekov's Gag.
 * "It's funny that pirates were always going around searching for treasure, and they never realized that the real treasure was the fond memories they were creating." So said Jack Handey in one of his Deep Thoughts segments. You'd be forgiven for thinking that the quote had anything to do with that One Piece manga/anime that was released later that decade.
 * Lily Tomlin hosted an early episode where the recurring puppet character Scred developed a crush on her. She awkwardly responded that being in a relationship with a puppet wouldn't be the best career move for her. One wonders nowadays if she would have responded better to a female puppet.
 * A sketch in 1995 had Ellen DeGeneres (played by Kids in The Hall regular Mark McKinney, who was also on SNL) & Anne Heche (Chris Kattan) on Oprah Winfrey's (Tim Meadows) show talking about their relationship, with the sketch implying that Heche wasn't really a lesbian and had only become one to get fame. Seeing as what happened several years later, SNL was on the ball with this one.
 * The Mirror Digital Short. Now, when did I last see Ellen Page trapped in a dream?
 * A season 36 episode featured a fake trailer for the movie Unstoppable. Denzel Washington (played by Jay Pharoah) asks Chris Pine (played by Taran Killam), "Where'd you learn trains, huh? Thomas the Tank Engine?" Couple months later, Cartoon Network's sketch show MAD came up with their parody of Unstoppable that also had a reference to Thomas The Tank Engine (only MAD's version combined Unstoppable with Thomas The Tank Engine).
 * On the season 24 Christmas episode hosted by Alec Baldwin, Jimmy Fallon takes Baldwin on a trip to the future which depicts what SNL will be like in the year 2011 (Fallon says the episode they're visiting is from December 12, 2011, which was a Monday this year). Even though there are a lot of things that are way off (the opening they used for the fictitious 2011 episode is not the one they used now, the cast does not include John Goodman [who hasn't appeared on SNL since season 28 when Dan Aykroyd came back to host] nor does it have older people in it [there are some that were born before or on 1975, like Fred Armisen, Kristen Wiig, Seth Meyers, and Jason Sudeikis, but most of the current cast members, such as Bill Hader, Andy Samberg, Kenan Thompson, Jay Pharoah, Abby Elliott, and Taran Killam were all born after SNL premiered in 1975], Don Pardo was not replaced with a robot [he's still the announcer, only he does all of his recordings from his home in Arizona], and the monologue stage is now modeled after Grand Central Station [the wrought-iron alley setting was retired after season 28]), there was one thing they got right:.
 * During the LeBron James episode, there's a sketch in which he's destroying some guy in one-on-one while trying to endorse a product. One of the taunts the overmatched guy makes is "Why didn't we get Dwyane Wade? He's actually got a ring!" A few years later, James and Wade would become teammates.
 * Eddie Izzard: "Everyone knows marijuana's a drug enhancement that can help you on track and field to come last in a team of "eight million other runners who are all dead." Or to win five gold medals.
 * His insistence that hopscotch is spooky Womens' Mysteries that allows them to escape The Grim Reaper becomes even more funny after seeing Corpse Bride, where "hopscotch" is the return word used in a specific casting of a visit-the-world-of-the-living-until-saying-the-return-word spell.
 * Mad Magazine had a Star Trek special issue around the time of the release of Star Trek Generations which included an introductory poem reviewing the history of the franchise up to that point: the final paragraph was devoted to wondering where the series would go from there. In particular, it wondered, "Would Worf and Sulu join up with the crew of Deep Space Nine?" Well, they got it half right...Sulu did appear on Star Trek Voyager...
 * Even more hilariously, when the Deep Space Nine crew timetravels into a classic Star Trek the Original Series episode, only one main crew member of the original Enterprise is not seen: Sulu. As he did not appear in the original episode.
 * The Generations parody also included a line about how Data hoped that in the next sequel, he'd be equipped with genitalia. Star Trek First Contact comes along and sure enough, Data insists to the Borg Queen that he is "fully functional"...
 * Except the second episode of the series revealed he was "fully functional" already. BEFORE the parody.
 * Radio Free Vestibule did a sketch called "Laurence Oliver for Diet Coke" in which samples of Laurence Olivier's voice are assembled into a testimonial for Diet "Koh-kuh Koh-luh". Funny, and much funnier after the release of Sky Captain and The World of Tomorrow.
 * An offhand joke in the MAD parody of Star Wars: Return of the Jedi noted that the final battle had everything but a kitchen sink, followed by a character remarking that he was wrong; the sink was on their side. Revenge of the Sith has a kitchen sink as an Easter Egg in its opening battle.
 * Knowing George Lucas, he probably read that parody.
 * In the commentary he explicitly mentions "everything but a kitchen sink".
 * Every line Angus Deayton ever read on Have I Got News for You that made fun of someone for a drug or sex scandal. YouTube commenters never miss a reference; even Ian Hislop and Paul Merton get in on it on the DVD commentary. (Paul, during a clip from the end of the first Christmas special, when a bunch of fake snow was dropped onto the set: "OH LOOK, what's all that white stuff falling on Angus?") The most infamous example: Angus asking John Simpson, after the Richard Bacon scandal, "What's your take on TV presenters doing drugs, then?"
 * In 2001 Adam Buxton and Joe Cornish spoofed a show about a family living in an Edwardian era house with a sketch about The 1980's House, where a modern family try to cope with being 'reduced' to living with primitive 1980s technology. In 2009 BBC Four present 'Electric Dreams', about a family trying to live with 1970s, 1980s, and 1990s levels of technology: 'Will they get used to tech-free bedrooms and embrace life outside the home or will they miss their 21st Century electronic distractions?'. Or, as Adam put it: "People in the 'eighties had to take two bottles into the shower!".
 * In Stephen Colbert's roast of the president at the the Washington Press Corps Dinner, he had a joke about what a maverick John McCain was. That was in 2006, before McCain ran for president with that as his major slogan.
 * In Norm MacDonald's last appearance on Late Night with Conan O'Brien, he talked about how Leno "outfoxed" Conan (Leno was starting the 10pm weeknight show before Conan at the time). A little less than a year later, it takes on more hilarity given the fact that Conan is yet again being outfoxed.
 * On the first episode of The Tonight Show with Conan O'Brien, Will Ferrell told Conan to enjoy the hosting the show while he could, and this was all "fleeting at best." Actually, this might be Depressing in Hindsight.
 * Then there was that "In The Year 2000" prediction that a comet will come and hit the Earth and that Conan's show would be canceled as a result. The only things Conan got wrong was the fact that a comet hit the Earth and that his show cancellation didn't happen in the year 2000 (more like ten years later).
 * Daniel Tosh once made a joke about how he wishes God rested on a Wednesday (implying that it is a useless day). Once Tosh.0 was moved to Wednesday it's funny for a different reason.
 * Bill Hicks' whole bit about Billy Ray Cyrus seems even funnier these days.
 * Denis Leary was once friends with Hicks until Leary released his album No Cure For Cancer, making Hicks feel Leary stole his material. Hicks died of pancreatic cancer.
 * George Carlin's already funny rant about airport security from You Are All Diseased came out in 1999. That is, before 9/11. After 9/11 and the recent increase in airport security to the point of public outrage, this bit will likely cause at least one death from hilarity.
 * During his "No Cure for Cancer" routine, Denis Leary joked about writing a self-help book called "Shut the Fuck Up, By Dr. Denis Leary". 10 or so years later, he would receive an honorary doctorate, allowing him to legitimately attach the name "Dr. Denis Leary" to a book. Which was not entitled Shut The Fuck Up, but rather Why We Suck. Though it used the same tone as the comedy routine implied it would.
 * During the Monica Lewinsky hearings, Chris Rock had a bit assailing Newt Gingrich as unattractive and accusing him of attacking Bill Clinton out of jealousy. He ended the bit by saying "Can you picture Gingrich saying 'I wish these ho's would back up off me and let a player play'." Considering the revelations that Gingrich was having an affair while persecuting Clinton and has had multiple affairs in the past, this bit fits this trope like a glove.
 * Al Franken's 1999 book Why Not Me? depicts a fictional version of the upcoming 2000 presidential election in which Franken himself becomes the Democratic nominee. He proceeds to hire an all-Jewish staff and his running mate is...Joe Lieberman. (His reasoning: he wanted to balance the ticket because "I'm Reform and he's Orthodox.") Lieberman in fact ended up being the Democratic vice-presidential candidate in 2000.
 * During the White House Press Correspondents' Dinner in 2011, Seth Meyer made a joke that Osama bin Laden went into hiding by taking up a show on political network C-SPAN. Within twenty-four hours, bin Laden was located and killed, and the joke - along with the President's reaction to it - became more infamous (though given bin Laden's very small fanbase, it remains funny).