I remember flying with a bloke early one morning and wondering why he kept on nosing the machine over gently into a shallow dive and pushing up towards Vne.
After a few occurrences of this, combined with his giggly conversation, I figured he was still p1ssed from the night before.
It surprised me because he had always struck me as a good and responsible aviator; obviously though he didn't know when to play the 'I know I'm not in a fit state to fly, I'll bite the bullet and ground myself until I'm sober' card.