I enjoyed a documentary HBO is running this month called “Casting By,” about the women (mostly) and men who have found the actors who became stars in various major motion pictures and television shows throughout the years. I was going to write about it, but Ken Levine — who knows a thing or two about showbiz after his years on “M*A*S*H” and “Cheers” — has said everything I would say, and more. Read his column here.