Autumn High Memories

Before Skumble Alteration
A popular manga written by a relatively obscure author known only as Hobbes. It follows the bland protagonist Taro-Kun as he attends Autumn Hills High, a high school set in the far future, and interacts with various characters, including the bored teacher, the bubbly love interest, the optimistic best friend, the bitter rival from a different school, the geriatric principal, the mean spirited bully, and as of recently, The Stabber. And, in one case, an Ur Cultist.

As the manga progresses, it gets weirder and weirder, as the author began to experiment with various storytelling tropes, with series four being the most controversial due to it suddenly taking a sudden focus on fighting animal testing and the fur industry. Afterward, it dived into hard conceptual science fiction, before fanfiction authors began adding their own chapters, most notably, Geiger.

Skumble Alteration
During one adventure in a battle against an Ur Cultist, one cultist got shot with a Skumble Blowdart imbued with Wild Magic, transporting the cultist into Autumn High Memories, altering the manga into a strange, dark manga, with strange tones and body horror.