Day 1: What are you responding to or inspired by when you write fanfic?
I suppose there are three primary things that lead to my writing.
1. If the creators leave something out, or don't resolve something to my satisfaction. If I'm wondering, "Why didn't they go into this more?" or "Why was this character this way?" See: WIDK
2. If I think two characters would be absolutely perfect together, but the creators didn't put them together. I feel like it's something that has to be explored, and I try to do it as realistically as possible. I try to go from a standpoint of, "Could this reasonably follow what already happened in canon?" See: Shadows, How Far, etc.
3. If I simply think, "Hey, wouldn't it be funny if....?" A lot of my humor pieces come from this place. See: IKIWISI, Fun and Games, etc.
For the most part, I'm inspired by/responding to characters. The original canon plots are very often secondary to me. I have to love the characters and want to explore their interactions and motivations more. I want to know what goes on in their heads, how they tick, how they relate to each other, how they'd respond in new/different situations. And I want to have fun with them.