Much like what I said about Hogwarts AUs, I think fandom fusions tend to be used " to play with "what's the most important facet of this character", "what's a hidden facet of this character that I want to explore", "what if half of them makes them a perfect fit for group 1 but the other half into group 2, how does that work?", "if I split this character away from the characters they are usually with, do they still become friends because destiny says so" etc."
All the things this character is, would they still be that way in this other way and place.
I've finished two proper fusion fics, I think fandom fusions just aren't the way my brain writes, I want to write more the situation that the characters are actually in.
One was done very much in the spirit of what I said up there,
For My Wings I've Been Searching, Tsubasa Reservoir Chronicles queer gen fic, where the original lgbtfest prompt was "Crossover: His Dark Materials fusion with any fandom, It’s hard to be closeted when people can tell what you are just by looking at your daemon.", but I wanted some world hoppers because I think having a daemon would really change you a lot.
The other one was not -
A Bad Night which was written for
opera142, and was wrestling fused into Raffles because I needed a reason for Jericho to be Regal's butler - and probably because I'd just been reading Raffles at the time.
( The other days )