IT WAS The Flintstones, the children’s cartoon about a prehistoric family, that promised viewers “a gay old time”.

The Simpsons, however, which recently beat The Flintstones by becoming the longest-running 30-minute animated television show, has gone one step further: it will “out” one of its popular characters as gay and give them a same-sex wedding.

The revelation was made at an annual comic book convention in California, attended by some 80,000 fans.

“We have a show where, to raise money, Springfield legalises gay marriage,” said Al Jean, producer of The Simpsons, referring to the fictional town where the show takes place. The gay episode is expected to be broadcast in January.

Mr Jean added: “Homer becomes a minister by going on the internet and filling out a form. A long-time character comes out of the closet but I’m not saying who.”

The last big mystery over a Simpsons plot came when a character was killed off — it turned out to be Maude, the wife of Homer Simpson’s relentlessly cheerful neighbour, Ned Flanders, who once opened a shop for left-handed people.

The most obvious choice of gay character would be Waylon Smithers, the obsequious aide to Montgomery Burns, owner of the Springfield Nuclear Power Plant at which Homer is an inept, beer-saturated safety inspector.

The show has already revealed that the bespectacled Smithers collects dolls and takes holidays at men’s singles resorts. He also lives in a gay part of town, has a Mr Burns screensaver on his computer and dreams of a naked Mr Burns jumping out of a birthday cake. Those who know the show’s gay secret, however, caution against rushing to judgment. Matt Groening, creator of The Simpsons, which began as a short “bumper” between adverts on The Tracey Ullman Show in 1987, joked with convention-goers that the gay character could be Homer.

Since its debut 17 years ago, The Simpsons has become one of the most successful television shows of all time. It is broadcast in 60 countries and earns an estimated $2.5 billion (£1.4 billion) a year from international syndication. Its cast, including Nancy Cartwright, a 44-year-old mother of two who is the voice of Bart Simpson, recently went on strike for a pay rise. They now receive an estimated $360,000 (£197,000) an episode, or $8 million (£4.4 million) for the 22-episode season.

Ms Cartwright will record some of this season’s shows from Edinburgh, where she is putting on a show for the Fringe festival entitled My Life as a Ten-Year-Old Boy.

The Simpsons is owned by the Fox television network, part of The News Corporation, which is the parent company of The Times.

Mr Groening teased convention-goers with the possibility of a Simpsons film but said that it would not be made until the television series finally ended. The Simpsons must outlast Gunsmoke, the Wild West series which survived from 1955 until 1975 to become the longest-running series of any length on television.

The Simpsons is almost as famous for its guest stars as its regular cast of characters, which include the family of Bart, Lisa, Homer and Marge. Guests for the next series may include the rapper 50 Cent, the comic actor Ray Romano (star of the popular Everybody Loves Raymond) and the Sex and the City star Kim Cattrall.

Meanwhile, speculation continues about the gay character with fans’ websites largely rejecting the “obvious” choice of Smithers in favour of everyone from Carl, Homer’s fellow nuclear technician, to Comic Book Guy, Springfield’s pony-tailed nerd.

Moe the bartender, Reverend Lovejoy and Principal Skinner (the high school head) are also seen as potential candidates. The show’s producers have not ruled out a lesbian wedding either.

PRIDE AND PREJUDICE

Batman, 1966 series: The producers wrote in a female aunt for the second series in the hope of quashing rumours that Bruce Wayne and Dick Grayson were gay

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