It this is not allowed by the mods, then please deleete.
I like approaching crossovers from a theoretical perspective. That is, I rarely write stories on a crossover these days, but instead write theoretical essays on how such things would flow and the mechanics behind it all. With a special focus on subtle (and overt) crossover that occur within the published media of a specific franchize.
Odd? Very.
Recently, I finally compiled an up-to-date Crossover essay regarding the 20 Canonical and EU crossovers that have occured within Buffy the Vampire Slayer and Angel. With discussions upon how that effects both the crossed media and the core of the Buffyverse.
I'll save how Secondary and Tertiary crossovers can aid in the construction of a world and how such work can expand ones understanding of said universe for another essay.
Enjoy!