I would like to share an email that I received in 2002 about Charlie Chan at the Opera, our Monday Night Chat Room Movie (8:00 PM to 10:00 PM [EDT], we start our movies/DVD's at 8:30).
I had sent an email about Boris Karloff's appearance in CC at the Opera to Sara Karloff's (and the only official) website for her father at www.karloff.com. (It's well-worth visiting.)
(Left to right: Bela Lugosi (Jr.), Sara Karloff, and Ron Chaney;
courtesy of www.lonchaney.com.)
She was kind enough to send me a reply on June 16, 2002:
Thank you for your lovely email. I always enjoy hearing from my father's fans.
I know from interviews my Father did that the set of Charlie Chan was sheer chaos with script changes every scene, actually being written as they were being shot.
There is a wonderful biography on my Father written by Scott Nolan in which that is one of the films he discusses.
Have a lovely summer.