Ok, this is 更多 of two questions, but still…

I believe a crackfic is a kind of comedy 或者 spoof of a story 或者 book 或者 film. Where fanfics are just in the world of another story, crackfics are comedic versions. That is the just I got but I could be mistaken.

Crackfic is where the writer takes something that isn't believable in some manner and tries to make it believable. The best known crackfics do fall under comedy and spoofs, but these aren't the best representation of the genre. Crack fic involves pairing two unlikely people together, working with a crack theory 或者 some other thing that people would think 你 are out of your mind to do. It gets its name from the fact 你 wouldn't think people would come up with these ideas unless they were on a sugar high, but other times they are very well thought out.