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Twenty years of The Simpsons? D’Oh! And yet Bart is still in fourth grade.

Dan Castellaneta has been the voice of Homer Simpson since the start and all these years later, Castellaneta is pleased the series has remained at the top of its game.

Click onto the video  for what Dan Castellaneta finds most gratifying about working on The Simpsons.

The Simpsons airs Sundays, 8:00 p.m. ET/PT on Fox.