He seemed so helpless, like a little lost puppy, and my heart just went out to him.

9 seconds sound clip from the Back to the Future movie soundboard.

You can hear this line at 00:16:32 in the Blu-ray version of the movie.

Quote context

[...]

- Anyway, if Grandpa hadn't hit him, then none of you would have been born.

- Yeah, well. I still don't understand what Dad was doing in the middle of the street.

- What was it, George? Bird-watching?

- What, Lorraine? What?

- Anyway, your Grandpa hit him with the car and brought him into the house.

- He seemed so helpless, like a little lost puppy, and my heart just went out to him.

- Yeah, Mom, we know. You've told us this story a million times.

- You felt sorry for him, so you decided to go with him to the Fish Under the Sea dance. No. Lt was the Enchantment Under the Sea dance.

- Our first date. I'll never forget it. Lt was the night of that terrible thunderstorm, remember, George?

- Your father kissed me for the very first time on that dance floor. Lt was then that I realized that I was going to spend the rest of my life with him.

[...]