They want more d'oh! The voices of The Simpsons -- Dan Castellaneta (Homer), Nancy Cartwright (Bart), and Hank Azaria (Moe, Apu) among them -- have been playing hooky for the past month while their agents try to wrangle raises of $235,000 per ep for season 16, debuting in September (the actors now make $125,000 apiece). So far, producer 20th Century Fox TV isn't budging (the cast staged a similar protest in '98 to boost their $25,000 salaries. Fox ultimately obliged). ''They are an incredibly talented bunch, as well as very well compensated,'' says a Fox exec. ''We're just not willing to go as far as they demand.'' A rep for the actors says, ''The Simpsons cast has not walked away.... Fox walked away from the negotiating table.''