What do actors do when dialog is designed not to be heard?

I was watching the Silver Linings Playbook tonight and the final scene made me think of this question. During the beginning of the final scene, which takes place in Pat Solitano Sr.'s house, Bradley Cooper is doing a narration. There is score music in the background. As we pan through the house, viewing most of the rest of the cast in some sports related get together, the camera ends up focusing on the character of Tiffany. Cooper's narration ends and the camera continues on to view Pat Solitano sitting in a chair. Tiffany comes over and curls up in his lap and the score hits its final crescendo, fade to black.

OK. So when Tiffany curls up in Pat Jr.'s lap, the two of them a speaking to one another. We don't hear the dialog. We're not really meant to. Would that unheard dialog be actual scripted dialog? Or would it read something like:

Scene 543: Pat in chair, Tiffany curls up in lap. Pat and Tiffany talk.

Or... would Bradley be telling Jennifer Lawrence a joke, or perhaps "Gee, you weigh more than you look" or?

EDIT: Actually, according the Silver Lining Playbook Script Rough Draft, Page 152:

TIFFANY SITS DOWN ON PAT’S LAP AND THEY TALK (we cannot hear them) and KISS.

So, what would they be saying?

dialogue screenplay

Best Answer

I'm not sure if I should post this as a comment, or answer, but it really depends on the movie.

In most cases that I've heard of, they just say unscripted things to provide the illusion of a conversation.

Example of a hilarious unscripted part is :
https://www.youtube.com/watch?v=SEVK3j4wJvU
In the episode, we hear 4 of the first instructions, then Martha fast-forwards, but David Tennant in the set has continued talking, so when fast-forwarded it will look like he's normally telling her other instructions.