Examples: Itchy & Scratchy from The Simpsons, The Scary Door from Futurama, or The Grand Inquisitor from Dostoevsky.
“The Wall” in Solar Opposites. It’s arguably better than the main story.
The main story has really picked up since Dan Stevens took over the voice of Korvo. IMO, it was a huge improvement. Also, the wall story isn’t as compelling as it used to be.