Is there a term for the opposite of the Chuck Cunningham Syndrome?

Question

Chuck Cunningham Syndrome refers to when a character simply disappears with no explanation and is treated in later episodes as if they never existed. I was wondering if there was a term, maybe "Sondra Huxtable Syndrome", for characters who just appear with no explanation?

Answer 1

In TV writing, this is called retroactive continuity, aka "retcon," where a character is introduced as if they had always been there, without explanation. You can learn more about it at TVtropes.org below!

https://tvtropes.org/pmwiki/pmwiki.php/Main/Retcon