I once had a boss like that, moodier than anyone I've ever known! She's be laughing with you one moment and then have her war-face on the next like you just kicked her cat or something. What I figured out was to stay aloof, then it seemed she never felt the need to put me in my place. Rather, it almost seemed like she was trying to make more jokes to reel me back in to her drama.

Oh no, Boss-Lady! Not falling for that again...