The programme which is seen by 60 million people worldwide, is starting to cause concerns for Groening.
"It becomes increasingly difficult as the years go by to keep on not only surprising the audience, but surprising ourselves," he said.
"When any character is as stupid as Homer Simpson, it's hard to keep surprising the audience."
Although the show managed to cause upset recently when it showed Rio de Janeiro as teeming with rats, monkeys
and street crime.
Brazilian tourist officials were outraged and
the show's executive producer was forced to apologise.
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