All that happened is that Don was nervous at the idea of meeting your parents and so he took a couple of drinks.
4 seconds sound clip from the The Lost Weekend (1945) movie soundboard.
You can hear this line at 00:46:34.393 in the Blu-ray version of the movie.
Quote context
[...]
- Thanks very much for your Philadelphia Story, Wick. Nice try.
- She doesn't have to. Just look at the two of us.
- Yes. What is all this covering up?
- Come on, Wick, she'd have found out sooner or later.
- Don's a little tight. Most people drink a little. A lot of them get tight once in a while.
- What I'm trying to say is I'm not a drinker. I'm a drunk. They had to put me away once.
- You see, that first time we met, I should have had the decency to get drunk... just for your sake.
[...]
