peanuthead

In the 1944 Cary Grant version of Arsenic & Old Lace, i could have sworn the body in the window seat was played by someone who would later -- or was about to -- become famous. Someone very tall. I thought Robert Osborne revealed this trivia in an A&OL introduction, but I can't find it anywhere and it's making me nuts!! Jimmy Stewart? Fred Gwynne? James Arness??? Doesn't fit any of them as far as I can figure... does anyone know?