I spotted this today in this DVD piece on 'Arsenic and Old Lace':
Frank Capra’s hilarious and fun adaptation is from the play of the same name. Originally filmed in 1941 Capra had to wait to release the movie until 1944 when the Broadway play had run its course. Alexander, Hull and Adair had been performing on Broadway for the roles of the Brewster siblings and were allowed eight weeks leave to act in the film. Boris Karloff played Jonathan in the play, but could not be spared being the star attraction, so the part was played by Massey who ‘looked like Karloff’. The part of Mortimer was originally offered to Bob Hope and Jack Benny before Capra settled on Cary Grant.
http://www.examiner.com/x-10199-Dallas-Movie-Examiner~y2009m7d11-Theres-13-bodies-buried-in-the-cellar
Does anyone know about the offer to Jack?
Yhtapmys