Oddest fanon? With such extreme bastardisations of the characters you couldn’t possibly begin to fathom what would be the most oddest.
You have comedic sketches portraying the scarlet sisters as children, series where Reimu is silent and kind, psychotic death-traps of Koishi having a ‘heart-throbbing adventure’ and even bizarre wrestling events.
Yukkuri shiteitte ne!
If I had to nail it on the head, it would probably be that crazy import of ZUN into Gensokyo having him as the most powerful God.