Hilarious In Hindsight / Family Guy

• Stewie pleading to FOX to at least let them stay on long enough to be syndicated in "Road to Rhode Island", which, thanks to its 2005 revival, being rerun on TBS and Cartoon Network's [adult swim] block, and eventually reaching off-air syndication, it has exceeded its goal.
• In "When You Wish Upon a Weinstein," Peter expresses how badly he needs help from a Jewish person. Later in season 8, in the episode "Family Goy," it's revealed that Lois is Jewish on her mom's side, and had to hide it so Carter can get into a country club that's notorious for banning anyone who's Jewish.
• The season seven episode "We Love You Conrad" has Stewie refer to Bruce Jenner as a beautiful woman. In April 2015, Jenner came out as transgender, and two months later, got gender reassignment surgery and is now known as Caitlyn Jenner. Stewie knew her true gender identity six years before anyone else did and even funnier when Brian tries to correct him saying "Bruce Jenner is a man." This gets lampshaded ten years and ten seasons later in the season seventeen episode "Hefty Shades of Gray".
• Miley Cyrus is revealed to be a robot in "Hannah Banana"; her 2010 album Can't Be Tamed actually features a song called "Robot". The lyrics just make it even more funny.
• In the episode "Family Guy Viewer Mail #1", Peter tells Diane and Tom Tucker to "Make like a Siamese twin and split, and then one of you die." Diane was Killed Off for Real in the ninth season premiere.
• One cutaway gag features Katie Holmes escaping from Tom Cruise, In June 2012, Katie announced she was divorcing Tom because he was too controlling.
• In "Screwed the Pooch" after finding out Brian didn't impregnate Seabreeze, he says he was looking forward to being a dad. Later in "The Former Life of Brian", it is revealed he has a human son (and in "Jerome is the New Black," one of the reasons why Quagmire hates Brian is that he never cares for Dylan, having only seen him once and bonded with while smoking weed).
• A 2007 episode contained a joke in which Carl Sagan's Cosmos was "edited for rednecks" by dubbing over an explanation of the Big Bang. In 2014, an Oklahoma City Fox affiliate just happened to interrupt Neil deGrasse Tyson's mention of evolution on the updated Cosmos. Not to mention that Seth MacFarlane is actually involved with the Cosmos reboot.
• Possibly deliberate; eight years after a cutaway joke about the implausibility of Liam Neeson playing an American cowboy because of his Irish accent and being in more UK movies than American ones, Seth MacFarlane cast him in his sophomore directorial effort, A Million Ways to Die in the West as an outlaw American cowboy (and, is considered by some, to be the only good part of the movie).
• "What Really Grinds My Gears" from Stewie Griffin: The Untold Story is very similar to You Know What's Bullshit?. Peter even kind of looks like a fatter James Rolfe.
• One cutaway gag had Iceman's wife catching him going to a gay bar. Nine years later, Iceman canonically came out as gay.
• In "Bill and Peter's Bogus Journey", a cutaway of "The Thing dating Lorena Bobbitt" features somebody finding The Thing's rocky penis. In Fantastic Four (2015), it was revealed that The Thing doesn't have any pants on and appears not to have any genitals, which makes this scene ironic.
• During the "post-movie" scene of Stewie Griffin: The Untold Story, Peter mentions that an episode he directed caused backlash because it centered on incest, which is exactly what happened in the season 12 episode "Fresh Heir" (only it had Chris about to marry Peter, not Chris having sex with Lois and Brian ranting, "Wrong! It's wrong!").
• In "North by North Quahog" Peter and Lois find a fictional sequel to The Passion of the Christ in Mel Gibson's home. In June 2016, it was announced that Mel Gibson would be making a sequel.
• In "The Tan Aquatic With Steve Zissou", Peter grumbles about getting Mega Bloks instead of bonafide LEGOs. Much later, Mega Bloks (since renamed Mega Construx) released an official Peter Griffin collectable figurine.
• The plot of "A House Full of Peters" makes Peter's Suspiciously Specific Denial about his having unwittingly fathered another child in "Don't Make Me Over" much, much funnier. For bonus points, the former episode took place after Peter's vasectomy, and the latter took place before.
• "Brian Sings and Swings", in which Brian meets Frank Sinatra Jr. and begins to perform on stage with him (and they are shortly joined by Stewie), has Peter mistakenly believe that Frank Jr.'s mother is Mia Farrow, even becoming a Brick Joke at the end of the episode when Farrow spanks Frank Jr. in front of an audience. In 2013, Mia Farrow raised speculation that Frank Sinatra could have been the biological father of Ronan Farrow, her son with Woody Allen.
• The episode "Patriot Games" had Peter join the New England Patriots and get fired after only one game. More than one person compared this to what happened to Antonio Brown in the real 2019 football season.
• In "Meet the Quagmires", in a parody of Back to the Future, Brian gives a performance of "Never Gonna Give You Up" in place of the original film's "Johnny D. Goode". The original Rickroll had already been circulating 4chan for at least a couple of months by the episode's release, but it still wasn't a well known phenomenon, and the episode had been in production for much longer. The Family Guy writers were merely making fun of the song for being a mediocre 80s chart-topper, yet they happened to do so just before an internet meme would cement the song in popular culture.
• One of the alternate realities seen in "Road to the Multiverse" is a pastiche of Disney's Renaissance Age, which delights Stewie to the point he wishes to be a part of that world. With Disney's acquisition of Fox in 2019, his wish has come true.
• This cutaway gag was about what would happen if Godzilla attacked a country that had already been devastated by something else. This would become the premise of Godzilla Minus One.