Arsenic and Old Lace is a 1944 American dark comedy film directed by Frank Capra, starring Cary Grant, and based on Joseph Kesselring's play Arsenic and Old Lace. The script adaptation was by Julius J. Epstein and Philip G. Epstein. Capra actually filmed the movie in 1941 because of star Cary Grant's availability, but it was not released until 1944, after the original stage version had finished its run on Broadway. The lead role of Mortimer Brewster was originally intended for Bob Hope, but he could not be released from his contract with Paramount. Capra had also approached Jack Benny and Ronald Reagan before learning that Grant would accept the role. Boris Karloff played Jonathan Brewster, who "looks like Karloff," on the Broadway stage, but he was unable to do the movie as well because he was still appearing in the play during filming, and Raymond Massey took his place. The film's supporting cast also features Priscilla Lane, Jack Carson, Edward Everett Horton and Peter Lorre. Wikipedia
Mortimer Brewster: Even the cat's in on it!