Ah---sorry for never explaining
Crack pairing. I think there was a thread about this, somewhere. It's basically a very unlikely couple.
For Example, A fic that had Clark and Lana (boo!) as a couple would be called "A Clark & Lana pairing".
But a fic that had, say, Clark and Aunt May as a couple would be a "crack pair", because whoever thought of that was obviously using---um---artificial sweeteners.
