rec req: crossovers

[wisdomeagle]

I have some essays in my brain about the writing of crossovers, but I want to avoid the temptation to use my own fics as my sole examples. So, I'm looking for crossover fics, both long and short, 'shippy and not. Good preferred, but readable is my only real criterion. Feel free to rec yourself, but only if you're open to discussion. Not, you know, bad discussion; I'm not looking to critique anything per se but say, "Look! These are issues that come up in crossovers, and several of the ways that people deal with them!"