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.
MG says that Homer and Abraham's middle initials are a token of admiration
for Rocky and Bullwinkle (Rocket J. Squirrel and Bullwinkle J. Moose),
whose initials were in honor of their creator, Jay Ward. Apparently,
as of episode AABF02, Homer's "J" stands for "Jay." Decide for yourself
which answer is more consistent.
According to MG, Bart's middle name is Jo-Jo, and not Jebediah as stated
previously in the _Rainy Day Fun Book_. One can only guess that some facts
got lost when the RDFB was made. The name was given to him by none other
than Nancy Cartwright.
 
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