Well, I'm a son of a gun.
4 seconds sound clip from the Holiday Inn (1942) movie soundboard.
You can hear this line at 01:32:03 in the Blu-ray version of the movie.
Quote context
[...]
- Well, I'm a dull, technical sort of a fellow.
- Perhaps if you'd wait and see Linda tomorrow.
- Oh, no, I want to see the finish.
- The success of you and Linda means a lot to me, pal.
- Say, why don't you be yourself. What are you up to?
- You remember how I suspected you when you came to live at the inn on Easter morning?
- Now I know he's up to something.
[...]