As I remember, when you lie flat on your back, you snore.
5 seconds sound clip from the The Best Years of Our Lives (1946) movie soundboard.
You can hear this line at 00:48:31.685 in the Blu-ray version of the movie.
Quote context
[...]
- And good night to you, Peggy. It has indeed been a great pleasure.
- By all means. I beg your pardon. Good night.
- We'd better wait and see if he gets in.
- I don't think he even knows if this is the right place.
- Don't ask. We want it to be a surprise.
- They make a lovely couple, don't they?
- Yeah, I think they'll be very happy together.
- Don't you remember? I'm Peggy.
- As I remember, when you lie flat on your back, you snore.
- Here. Where's your hand? Here. Give me your hand.
- Night.
- Night.
- Got a turnaround at 4 o'clock.
[...]