It has been on air since 1989 - but some fans of The Simpsons are only just learning why creators changed a key detail about one of its characters.
When making his first appearance in episode three of the first season, Homer's Odyssey, Waylon Smithers, who works as Mr Burns' personal assistant at the Springfield Nuclear Power Plant, has black skin.
However, in later episodes, his skin colour changes to yellow, making fans wonder why the creators decided to change his race. While some people believe the creators changed his skin colour on purpose, others admit to having never noticed this detail.
One confused Reddit user said: "Apparently Smithers used to be black..." While another added: "Today I learned that Mr Smithers of The Simpsons was originally black, but was changed to white because the staff thought it 'would be a bad idea to have a black sub-servient character'."
But according to creator Matt Groening, his change in skin colour was simply a mistake and he was always meant to have yellow skin. In an interview with TMZ, he said: "At the time we didn't have enough money to do retakes."
Commenting on this, one social media user said: "This was a fairly common thing in the early going in Bart the Genius you can see Milhouse has black hair, and there are numerous other variations from characters. It was part of the charm of an animated series in the early 90s that was still being hand drawn and painted.
"I actually miss (and Matt Groening has stated this too) the hand drawn style and I wish they weren't forced into using computers. They fought that for as long as they could. Homers over exaggerated motions and out of proportion body really enhanced the comedic effect."
Another user said: "I know there is one episode in which a character walks out of the room black and walks back in two minutes later white but can't think if Smithers was that character?" A final user added: "Colouring mistakes like that were common in the early seasons.
"Aside from the black Smithers incident, the ones I remember right offhand are one of Bart's friends changing race and hair colour from one shot to the next in the first episode, 'Simpsons Roasting On an Open Fire.' The switch happens when they're in the mall spying on Homer as Santa.
"In the season three episode 'Stark Raving Dad,' the Michael Jackson episode, Groundskeeper Willie is mistakenly coloured black in a crowd scene on the lawn in front of the Simpson home."