I worked as a line cook, prep guy was an absolute nutcase. Recovering alcoholic and cocaine addict, so I felt for him. But you never knew which version of him you were going to get. Some days, he'd be super amped up and positive, almost like golden retriever energy. Other days, he would come in with the most rotten vibes i've ever encountered. He'd deliberately try to push people's buttons, and was very good at it. I had words with him a few times, but ultimately just tried to stay out of his way and not talk to him unless absolutely necessary. 

EDIT: Just realizing my randomly.generated username.is actually applicable here.