idiom. Go cuckoo bananas; go slappy walnuts; go mentally wacky; go overnight postal; sprinkle crack on one's cornflakes.
Real citation: "Why leave it up to a couple of people, with no support? Especially people who are likely to go psycho bugnuts as they all apparently do?"
(Daniel, "Live Together, Die Alone," page 16, Television Without Pity, http://www.televisionwithoutpity.com/story.cgi?show=136&story=9402&page=16&sort=&limit=)
Made-up citation: "Since getting a puppy, litterbugs drive me six shades of psycho bugnuts--because he eats everything and then licks me. Essentially, your trash is licking me. Why don't you just smear it directly on my face?"