Clarence Bouvier
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Clancy Bouvier is the deceased father of Patty and Selma Bouvier and Marge Simpson and the husband of Jacqueline Bouvier. His first appearance was in the episode "The Way We Was". He didn't appear again until Fear of Flying where it was revealed that he was one of the earliest male flight attendants. The cause or time of his death is undetermined, but it occurred some time after Marge married Homer as he got her a "white-noise machine" to help her deal with his death according to Jazzy and the Pussycats. The only reference to Clancy's death is in Treehouse of Horror III, where a King Kong-like Homer is seen eating him.