While I have not trained the crazy monkey per se, I have seen it described as bringing up your arms near your head with your elbows ending up in front of you, and your hands going over the top of your head as if you were brushing your hair back. The purpose I believe is to make the opponent's strikes hit your elbows, injuring his hands. This is a transitory position as I understand it, seeing as your ribs are fairly exposed whilst in that position. Seems like it would be effective against a headhunter, though.
Hope this helps.