I have absolutely no idea if what I'm about to write is considered a crackfic but it's about Amanda Seyfried and Shiloh Fernandez and they were both in Red Riding Hood together?
I've written a crackfic - at least, I think it's a crackfic - called Mibba! At The Disco
I came about writing it when, for a competition I was doing, write a parody of another person's fandom. Their main fandom was Panic! At The Disco, which I knew nothing about, so I decided to throw in some Mibbians for added hillarity.
I love reading crackfics, but when it comes to writing them, I feel you have to be in the right frame of mind to go about it, otherwise events can often just seem forced, particularly in humourous fics.