The Fluffy Bunny Nice Nice Club (FBNNC for short) is a nickname for rabid anti-Mormons.
The name came from a debate a few of us bloggernacle regulars were having with the anti-Mormon zealots over at Mormon Coffee — a “counter-cult” blog run by a bunch of so-called Christian wackos who spend their lives trying to destroy Mormonism. One of the nutjobs over there wrote a post complaining that we Mormons call them anti-Mormons. (No, seriously, he really did.) John C. (who blogs at FPR and BCC) wrote a comment suggesting maybe they would prefer to be called the Fluffy Bunny Nice Nice Club instead. The anti-Mormon jihadists at that site didn’t find that snark amusing but I did so I started using it on the rare occasions when I write a post related to the FBNNC or Calvinism.