One possible theme is unrequited love. Snape loved Lily deeply, and their Patronuses, both being doves perhaps in some fanfictions, could symbolize that love. His Patronus could be a constant reminder of his love for her, even though she was with someone else.
In a fanfiction, Snape's Patronus could be the key to saving Lily from a dark magic curse in an alternate universe. Since the Patronus represents love and protection, Snape's doe Patronus might be able to break the curse that has trapped Lily's soul. As he sends his Patronus towards her, it glows with a powerful light that gradually dispels the dark magic surrounding her.
In fanfiction, one reason could be the Marauders' bullying of Snape. They often target him with their pranks, which are sometimes cruel. Lily, being Snape's friend (at least for a while), might despise the Marauders for their treatment of him. Also, the Marauders' cocky attitude might be off - putting to both Lily and Snape.
Snape's patronus being a doe in fanfictions often because it was his love for Lily that was a central part of his character. In the original story, his doe patronus was a symbol of his love for her. Fanfiction writers like to explore this aspect further, so they keep using it as it is such a powerful and poignant symbol of his unrequited love.
James' stag Patronus is a symbol of his adventurous spirit. Stags are wild and free, and James was always up for an adventure. It also reflects his protective side, as stags can be very protective of their herd. Lily's doe Patronus represents her nurturing side. Does are often associated with motherhood and care, which was a big part of Lily's character. Also, the contrast between the stag and the doe in their Patronuses is like the yin and yang of their relationship, showing how they complement each other.
Well, in some fanfictions, it could be because Snape's actions towards her friends in the original story. Maybe the fanfic writer wants to explore a different side of their relationship where Lily has had enough of Snape's dark arts fascination or his association with the wrong crowd at Hogwarts.
People are drawn to it because Snape's love for Lily was so deep and unrequited in a way. Fanfiction writers can play with different scenarios, like what if Lily had returned his feelings. It allows for a lot of creativity.
Well, it really depends on the fanfiction author's creativity. Some might give her a Patronus that reflects her own unique personality traits. For example, if she's portrayed as very brave and fierce in a particular fanfic, her Patronus could be a lioness, representing her courage and leadership. Another possibility is that it could be a bird, perhaps a phoenix, which would tie in with the magical and powerful nature often associated with the Potter family.
One interesting Snape patronus fanfiction is 'The Silver Doe's Secret'. It delves into the significance of Snape's doe patronus and its connection to his unrequited love for Lily. Another is 'Snape's Patronus Revelation' which explores how his patronus might have changed over time due to different events in his life.
Well, a lot of fanfictions depict Snape's love for Lily as a silent, internal struggle. He doesn't always show it outwardly, but it's always there, burning inside him. Some stories show how his love for her makes him protect Harry, not because he likes Harry, but because Harry is a part of Lily. This love is also sometimes shown as a complex emotion that is intertwined with his sense of self - worth. He feels unworthy of her love, but still can't let go of his feelings, and this internal conflict is explored in great detail in many fanfictions.