Piven Back on Broadway

2/27/2009 10:06 AM PST
Jeremy Piven -- now famous for bailing on Broadway -- made it a spectator sport last night ... and ran smack into one of the co-stars who was also a victim of too much mercury.

Piven was mum as he left Will Ferrell's show -- ditto for former "Speed-the-Plow" co-star (and "Mad Men" cast member) Elisabeth Moss.