Do you like crossovers? What is it about crossovers that you like/dislike? What fandoms were in your favourite?
Going to have to agree with dotKarma. If they're good or otherwise cracky, yes. If not, it can go horribly, horribly wrong. Basically, if they're good, then it's interesting to see how the two (or more) fandoms play off each other and actually fit together... or, alternatively, how they totally don't. Additionally, crossovers have the potential of being cracky or otherwise answer the interesting question of, "What if X was in Y?" However, all too often, authors choose two fandoms that are completely incompatible and, rather than try to honor that and use it to make the story more interesting, they simply mesh things together in a sloppy soup, usually by completely ignoring the original canon of one or the other. For example, there's the ever-popular Naruto-and-friends-are-Pokémon-trainers concept that's pretty much actually a whole pile of, "These are original characters who just happen to have the same names and look somewhat like these other characters." In other words, you're dealing with multiple fandoms, and you just have to make an effort to remember that when writing a crossover.
As for favorite fandoms, there was a fic on a long and pretty dead site that I loved and (even though looking back on it, its language use was pretty horrific) still think is awesome in terms of concepts was a Sailor Moon/Pokémon crossover in which Jessie and Misty turned out to be Sailor Scouts (Sailor Comet and Sailor Nereid, respectively) who were awakened because Malachite kidnapped the main Scouts. It was full of sparklies.
Other than that, there's
this, which is a crossover between
The Hitchhiker's Guide to the Galaxy and
Doctor Who that just worked and was probably the best tribute-to-a-dead-celebrity fic I've ever read.
