- Hello.
- Why, hello. This is quite a surprise.

5 seconds sound clip from the Back to the Future Part III movie soundboard.

You can hear this line at 00:48:59.445 in the DVD version of the movie.

Quote context

[...]

- All right, Marty, you all set?

- Yeah. Yeah. Go!

- Train pulling out of the station! Coming up to the switch track! Stop at the switch track! Throw the switch!

- Pull up to the DeLorean! Pushing the DeLorean up to 88 miles per hour!

- It couldn't be simpler.

- It's Clara. Quick, cover the DeLorean!

- Hello.

- Why, hello. This is quite a surprise.

- Well, I hope I'm not disturbing anything.

- Oh, no, no, we were just doing a little model railroading.

- Emmett, when my bags were thrown from the wagon, my telescope was damaged. And since you mentioned an interest in science, I thought you might be able to repair it for me.

- I would pay you, of course.

- Oh, no, no, no. I wouldn't think of charging you for this.

[...]