It's 1999, and Homer Simpson is spending his night the same place he usually does - nursing a pint in Moe's Tavern.
This time, however, he is joined by a rather surprising drinking partner; none other than renowned theoretical physicist Professor Stephen Hawking.
Having listened intently to Homer's theory "of a donut-shaped universe", the good scientist notes that it is certainly "intriguing".
Seeing one of the world's greatest minds guest-starring in a family cartoon and sending himself up in the process was as joyful as it was unexpected at the time. But the presence of Hawking, who has passed away at the age of 76, served a far greater purpose than just entertainment.
Surreal gags - but a serious lesson
Professor Hawking once noted that "as many people know me through The Simpsons as for my science".
And it's fair to say that his debut appearance on the show had quite the impact.
In 1999 episode 'They Saved Lisa's Brain', the titular child prodigy takes a stand against the rampant anti-intellectualism she notices eveywhere around her.
First she rails against Springfield's celebration of stupidity in a letter. Then she assembles a group of fellow brainiacs in an attempt to instill a new state of order on the town.
When they ultimately seize control, this IQ-heavy cabal's attempts to stamp their lofty ideals on everyone else result in division and chaos. A sort of totalitarian, culturally-elitist regime ensues; where only classical music can be played in public, and Dr Hibbert wants everyone to gulp down broccoli juice.
Enter a thoroughly unimpressed Hawking, who castigates the 'alphas' for their arrogance, and condemns their "utopia" as a 'fruitopia'.
"I don't know what is the bigger disappointment," he laments. "My failure to formulate a unified field theory - or you."
Amid surreal gags involving Inspector Gadget-like gizmos ("helicopter blades would be very useful", and "I don't use a boxing glove - though sometimes I'm sorely tempted", Hawking later joked), he ultimately imparts a crucial life lesson to Lisa.
"Sometimes the smartest of us can be the most childish."
A landmark moment
In a Twitter post today, executive producer and Simpsons showrunner Al Jean was one of many to pay tribute to Hawking, saying he had "a sense of humour as vast as the universe".
Anecdotes from the time speak of Hawking's enthusiasm for his guest role; how technicians worked around the clock to repair a broken wheelchair so he could make the recording session - so keen was he to be involved.
Hawking enjoyed the experience so much he went on to star as himself in three further episodes: in 2005, 2007 and again in 2010.
In a 2005 interview, he described his appearances on show as "great fun". But he also noted that "The Simpsons have treated my disability responsibly".
Homer may attempt to get Hawking to pick up his bar tab by impersonating his famous synthesised speech. But he gets a boxing glove to the face for his trouble.
It was, in many ways, a landmark moment for the representation of disability on screen. At the time The Simpsons was watched by more than 13 million people in the US alone. And here was a prominent, celebrated man who happened to be in a wheelchair, guest-starring in a pop culture phenomenon.
"The appeal of The Simpsons is that the characters display all the traits we see in themselves," Hawking later remarked.
"I accepted immediately, because I thought it would be fun. And because The Simpsons is the best thing on American television."
Voice of reason
Perhaps the most apt thing about Hawking's first appearance on The Simpsons is how it reflected his attitudes to the world, the wider universe, and people.
It's an episode about the perceived clash between the 'intellectual elite' and the 'ignorant public'; where the scientist acts as a calm, unifying voice of reason.
Homer is one of television's great lovable idiots. A man whose sheer ignorance is rivaled only by the size of his appetite.
And yet rather than dismiss him out of hand or castigate him for his bizarre donut theory, Hawking considers it carefully and engages with the man.
Perhaps it's not surprising that Hawking's on-screen depiction would rail against Mensa-imposed tyranny, given that he once remarked: "People who boast about their IQ are losers."
Two other quotes from the late, great physicist perfectly sum up his decision to appear on this episode of The Simpsons.
"The greatest enemy of knowledge is not ignorance, but the illusion of knowledge," he once famously said.
He also noted that: "Life would be tragic if it weren't funny".
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This article originally appeared on our sister site, iNews.