Marty, you're beginning to sound just like my mother.
5 seconds sound clip from the Back to the Future movie soundboard.
You can hear this line at 01:18:17 in the Blu-ray version of the movie.
Quote context
[...]
- I swiped it from the old lady's liquor cabinet.
- Yeah, well, you shouldn't drink. Why not?
- Because you... You might regret it later in life.
- Marty, don't be such a square.
- Everybody who's anybody drinks.
- Marty, you're beginning to sound just like my mother.
- We're going to take a little break, but we'll be back in a while, so don't nobody go nowhere.
- Marty? Why are you so nervous?
- You mean like how you're supposed to act on a first date?
- Sort of.
[...]