User blog comment:SouthParkKelly/Ralph Wiggum's death/@comment-961279-20190404000134

I think the people who make the show said it takes place in something like a "flexible continuity", which means that they can change things as they want to, even if it contradicts what they did before. The Treehouse of Horror specials have a lot of characters dying, but they come back anyway.

The only time a death might be permanent is if the voice actor dies. Nancy Cartwright voices Ralph, and she's still around.