To "plug the pig's ass" is to set in motion a chain of events which will result in an unfortunate, disastrous or hilarious outcome to the person plugging the pig's ass.

in slang: to plug the pig's ass is to fuck yourself over

It’s an acronym standing for Can’t Remember A Fucking Thing. It’s usually used to describe embarrassment at being unable to remember someone (CRAFT moment); going onstage as the lead in the latest theatrical performance and your mind goes completely blank (CRAFT situation); the next morning after a night when you got pissed as a fart and woke up in bed cuddling a traffic cone and a string of fairy lights wound round your prick.