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.
The "Treehouse of Horror" series is, according to MG, non-canonical and as
such the writers can do whatever they choose, such as put Mr. Burns'
country home in Pennsylvania, have the family appear to have long forked
tongues, or give Bart a twin brother named Hugo.
 
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