Trick or treat.

3 seconds sound clip from the Breakfast at Tiffany's movie soundboard.

You can hear this line at 01:20:59 in the Blu-ray version of the movie.

Quote context

[...]

- Come on. Don't be chicken.

- Anyway, you've never done it, and it's your turn.

(HOLLY BLOWS TOY TRUMPET)

- I can't see.

- Hi, cat. Lady of the house at home? Holly?

- Trick or treat.

- You're crazy. You know that, don't you? But I love you anyway.

- 2-E. I've got to talk to you.

- You want a drink?

- If this is going to be a serious discussion, and suddenly I'm terribly afraid it is, you're going to have to take off that ridiculous mask, or else I'm going to have to wear one, too.

[...]