In other fan comics, Patchouli is considered a hikikomori due to her apparent habit of spending all her time in one room (the library) and rarely ever stepping outside. She would only have to keep this up for 6 months to meet the time span given in the definition, and she's been living like that for the past 100 years.
Patchouli has been rumored to be the inspiration for the character Yue Ayase from the manga Negima! Magister Negi Magi. Like Patchouli, Yue is a short, quiet girl with long purple hair, an unexcitable personality, an affinity for books (she is a librarian) and magic (she is also known to dress in a witch outfit similar to Marisa's).
In the doujin anime A Summer Day's Dream, a book labeled Wikipedia can be seen in Patchouli's Library
In fanon, she is sometimes seen paired with Marisa. Because of this Alice sees her as an enemy and treats her as such.
Based on the profile picture that ZUN draw in the game Embodiment of Scarlet Devil, many fan arts had Patchouli's dress drawn with purple/violet/lavender and white stripes, even though afterwards ZUN had claimed her clothes never have stripes imprinted on it, this explanation even led to several fan theories that Patchy had some kind of chemical liquid spilled on her dress before the incident of the scarlet mist , causing her dress to have purple stripes, then the color starts to fade away afterwards, making to the explanation that why her Scarlet Weather Rhapsody in-game portrait doesn't show stripes on her dress.