Far rope munches britain fantastic originated in a thread suggesting that everyone on /oat/ should go onto Omegle and parasprite everyone there with ponies. Another user replied to the original post with a sarcastic comment about how much that would improve Ponychan's reputation. OP replied that /oat/ was being slow lately, so they needed to go out and get more territory. Aforementioned other user replied by mentioning that there are other ways to convert people to bronydom that don't involve paraspriting.
Now, this thread was against the rules, because Ponychanners are not allowed to raid other sites. Thus, a tactical mod had been called in. !!Celestia arrived right on cue, deleting the thread. He left a message beforehand, though. Thus, Far rope munches britain fantastic was born.
Where is it now?
Far rope munches britain fantastic is used sparingly as a kind of inside joke or secret phrase amongst channers. It appears way less around ponychan ever since the thread was baleeted.