Thread:Solipsius/@comment-25832710-20150821160907/@comment-25832710-20150821223534

That's a non-canon future episode. Non canon are not continual based, like the Treehouse of Horrors.What happens in non cannon is not continued on the later episode, it's if they never happened. On it's page here it states on top :This episode is considered non-canon and the events featured do not relate to the series and therefore may not have actually happened/existed.

It was make years before Edna was even thought of to be deceased on the show. Future episodes always contradict things, past and later episodes.