What do The Flintstones, Monty Python's Flying Circus, The Brady Bunch and Sgt Pepper's Lonely Hearts Club Band all have in common? And for that matter horror classic Nightmare on Elm Street, Dr Strangelove, physical theatre troupe Blue Man Group and 1960s spy spoof Get Smart?
You'd have to have been paying very close attention to The Simpsons over the past 25 years to have noticed the link. All of them have appeared in the traditional opening couch sequence in each episode. And that attention to detail is one of the main reasons the show has worked (and, partly, built its massive audience).
"Matt Groening’s iconic animated series turned hyper-referentiality into an art form, regularly packing in throwaway references to high and low culture right from the start," wrote Darren Franich in Entertainment Weekly. The Simpsons began as a kind of updated version of The Flintstones, the 1960s primetime cartoon caper that stuck a pretty standard sitcom formula in a Stone Age setting; even Groening's concept was a reference to something the audience would have recognised from their childhoods.
In those early Simpsons seasons – the animations more crudely drawn, the voices not quite as realised, the writers still fleshing out the family's personalities – there were flashes of this pop culture mining. But it's around the third season (1991-92) that it starts achieving the high notes that, arguably, made the comedy the decade's best.
That's perfectly encapsulated by the opening of the episode Bart's Friend Falls in Love, where Bart Simpson steals a jar of pennies from his dozing father. The entire scene is a glorious pastiche of the opening of Steven Spielberg's Raiders of the Lost Ark (itself a knowing tribute to those rough-and-tumble Saturday morning matinees Spielberg loved as a child), complete with Homer resembling a giant boulder in an epic chase down the stairs. It remains, more than 20 years later, one of the show's great, laugh-out-loud moments.
Every Simpsons fan will have their own favourite – for me, it's pretty much all of the season six cliffhanger and season seven opener split episode, Who Shot Mr Burns? It’s a Dallas homage that also packs in references to the Mambo Kings, Hitchcock's Vertigo and in Homer's cellmate Dr Colossus, every B-movie mad scientist ever. But The Simpsons’ enduring appeal – even if long-time fans might sniff that its best days are long behind it – is that it's much, much more than a collection of pop culture jokes.
"The Simpsons took [that referential humour] mainstream through just being a good show," says Christopher Irving, a pop culture historian and writer. "It's that simple: the pastiche, parody and inclusion of pop culture isn't what the show is built around – the show is built around relationships, which is what makes the Simpsons themselves believable enough to love."
Irving believes the show also celebrates some of the arcane geek culture that the programme’s writers are clearly fans of – while most people are likely to spot the references to Star Wars, Jaws and Close Encounters of the Third Kind, there are many references that appeal to a much more selective audience.
"Oh, God, yes. Look at comic book guy; sure, he pokes fun at the stereotype of the obsessive comic book fan, but that works because people like him really do exist," Irving says. "The 'geek culture' aspect of the show might not have worked without the production getting the real people on board for guest voice spots."
British cultural historian Christopher Cook believes The Simpsons has some strong links to the past – and not just TV. "You could argue that this is already a strategy developed by Pop artists – Richard Hamilton, Roy Lichtenstein and Andy Warhol, to name three. However, it does seem to me that The Simpsons is the television series that really embraces the idea," says Cook. "It may be significant that The Simpsons were created by Matt Groening who began his career as a cartoonist, so that he would clearly be across the work of, say, Lichtenstein.”
"But I would suggest that you also need to see The Simpsons as one the very first postmodern TV shows developed for mainstream US TV,” Cook says. “Someone once defined postmodernism as an 'aesthetic of quotations’, in other words it collages material from pre-existing works in unlikely ways. And the ‘glue’ that holds the assemblage together is irony, knowing where the references come from and how they have been replaced. I see a lot of that on The Simpsons.”
For all ages? / Generation gap
The show perhaps betrays some of its interests and influences, which definitely seem to stray into the geekier spectrum, says TV writer David Stubbs. "Matt Groening once boasted, ‘The Simpsons is the counterculture.’ I think that’s maybe truer of earlier [seasons] than more recent ones," he says. "And I think they only go so far. Groening’s favourite ever album is Trout Mask Replica [by Captain Beefheart] but I don’t think he’d feel able to get away with Captain Beefheart references on the show. Sonic Youth, yes…"
But is there an inherent problem with all these knowing pop culture references? Perhaps. Allusions to childhood adverts, arcade computer games and pop songs played on the radio long ago are powerful because they evoke such rich memories. And yes, if you're a 21-year-old watching those early Simpsons episodes now, all those references are a Google search away. But that doesn’t equal emotional resonance.
Stubbs agrees, citing a long-running Simpsons character based on Jack Lemmon in Glengarry Glen Ross that perhaps resonates best with those who have been exposed to this kind of material and not had to actively seek it out. "What concerns me slightly is that this current generation isn’t so inevitably steeped in old movies, wouldn’t necessarily get a Hitchcock reference because they didn’t grow up with this stuff on mainstream channels growing up. Now it’s farmed off to DVDs or film channels."
And while current viewers may adore the show for its knowing references, that could possibly be a problem for people coming to it in later years. "I Love Lucy, The Andy Griffith Show, The Mary Tyler Moore Show, Cheers and other pre-’90s sitcoms didn’t start to seem dated or irrelevant for decades," Matt Zoller Seitz wrote on Salon, "probably because they kept the pop culture references to a bare minimum. The more recent hit comedies are starting to exude that expired fish stench while they’re still on the air. Can a show still call itself a comedy if you have to explain why it’s funny?"
But Cook doesn’t believe The Simpsons’ jokes will wear thin anytime soon. “There’ll be PhDs and ‘guides’ galore to help people through The Simpsons. More seriously since it seems almost certain that The Simpsons will achieve cult status, that future generations will want to unravel the programmes and understand their referencing.”
If you would like to comment on this story or anything else you have seen on BBC Culture, head over to our Facebook page or message us on Twitter.