But that impressive run of an intact cast may finally be coming to an end.
Shearer wrote that he wanted "the freedom to do other work." Al Jean, executive producer and show runner, later tweeted that the actor's roles would be recast if he did not return.
Shearer's exit might not be settled, though.
On Thursday morning, one of the men responsible for bringing "The Simpsons" to TV sent out a tweet asking Shearer to return to the negotiating table to work out a return to the show.
"Hey, we tried," wrote veteran TV producer
Of course, contract disputes are nothing new in Hollywood, where egos often match the size of the paychecks. The courtrooms of Los Angeles and Santa Monica are filled with the fruits of entertainment-industry dealmaking gone bad.
But any potential change to "The Simpsons" shakes up pop culture, because of the show's iconic status and uncanny ability to keep virtually all its key players intact for more than a quarter-century.
This is not the first time the voice actors have butted heads with the studio. In 2011, a rancorous pay dispute led to a 30% pay cut for Shearer and the others, although they still earned a reported $300,000 per episode. That made them among the best-compensated actors on TV.
The Shearer dispute shows how Twitter is increasingly being employed in high-stakes negotiations over TV star contracts, fulfilling a role that used to be served by trade papers and gossip columns.
"Harry put it on Twitter in hopes fans would pressure the producers," said Howard Bragman, a veteran Hollywood publicist not directly involved with the major parties. "Most of these things are done by agents, lawyers and managers, very privately and discreetly.
"He's trying to get his fans to rally behind him. And he's not talking about money, he's talking about his artistic freedom, which is the smart thing to do," Bragman added.
"'Show will go on, Harry will not be part of it, wish him the best,'" Shearer wrote, passing on a message he said came from an attorney for Brooks.
"This is because I wanted what we've always had: The freedom to do other work," he added.
Shearer later added that his exit "wasn't about money."
Jean then tweeted that Shearer had passed on a deal the other five other regular voice actors had accepted. That deal, he said, would have allowed Shearer to pursue other work as he has always done. Shearer's tweet was "confusing," he wrote.
"My dream in life is for someone to treat me the way the Simpsons treated Harry," Jean added.
A spokesman for 20th Century Fox Television, which makes the show, did not return an email seeking comment.
Shearer would not be the first actor to exit abruptly from a hit cartoon. Isaac Hayes, who voiced Chef on "South Park," suddenly quit the series in 2006.
"The Simpsons" is the longest-running series in prime-time TV history and has delivered more than
$1 billion in profit to
Times staff writer Patrick Day contributed to this report.
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