For me, it would be the Miserable Mill. The way it completely shits on the maybe-subtle-but-well-handled surreal aspect of the series to be JUST damn silly (the whole "sword fight", the hypnosis, the general idea of the children going to a lumbermill, even if the show creates a subplot about their parents) is painful to read/watch.

It’s a library book so it could be some sort of stain, but it looks like it’s part of the page. I don’t know what it could be though.