An interesting story. I have heard of 'personal' fictional beings manifesting around all sorts of stimuli. Trauma and the like. Though in the case of soulbonds it sheds light on another peculiar area of this topic. Soulbonding if you don't know is when a fictional being bonds to the mind or soul of a person. Either temporarily or permanently.
Though permanent stays are a bit more uncommon. Many people can have brief soulbonds throughout their life. Some people can even call fictional beings from other realms. It's highly likely fiction spawn are an umbrella of phenomena.
1:Real beings from other realms interracting with people they decide to interract with[soulbonds]
2

sychic manifestations given life, either through one or more people. These psychic manifestations seem to ignore time based causality slightly. Sometimes manifesting before the media in question even exists.
3:A bit more uncommon and something i'm actually trying to research. A fictional being bonding to a certain aspect of our reality. Such as the internet or certain liminal spaces or concepts.