Arsenic and Old Lace (1944)
Not only one of the greatest dark comedies ever written, but a black and white classic, starring movie legend Cary Grant. In this particular scene, he finally sums up the courage to admit to his fiance just how stark, raving mad his entire family is.
Memorable Arsenic and Old Lace quote:
“Look I probably should have told you this before but you see... well... insanity runs in my family... It practically gallops.”