This article is from the The Simpsons FAQ, by Ondre Lombard wakkojr@nospam.wcat.com and Andrew Gill superluser@mail.rit.edu with numerous contributions by others.
When Dan Castellaneta originally began voicing Homer, he basically imitated
Walter Matthau to get the voice. However, Dan reportedly had trouble with
certain emotional registers and intonations with the voice, so beginning
with Season Two, he changed it slightly to create its present sound.
-> According to David Silverman, episode 7F22, "Blood Feud," is when Homer's
character began to gradually change into what it is now. (Notice that the
"letter" Troy McClure gets in 3F31 about Homer's stupidity is answered with
clips from each season of Homer doing stupid things, beginning with the
second season episode "Blood Feud.") The Tracey Ullman Short "The Pagans"
he sets as the point where Bart's character became set as the brat everyone
knows and loves.
 
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