- Why would I tell Mom?
- 'Cause you tell Mom everything.
- No, I don't.

5 seconds sound clip from the Donnie Darko movie soundboard.

You can hear this line at 01:01:55 in the Blu-ray version of the movie.

Quote context

[...]

- I just want it to be at a time when it...

- When what?

- When it reminds me just...

- When it reminds you how beautiful the world can be?

- Yeah.

- And right now there's some fat guy over there staring at us.

- I don't think telling any woman to forcibly insert an object up her anus is something that should go without consequence.

- I think we should buy him a moped.

- I think we should get a divorce.

- You aren't gonna tell Mom, are you?

- Why would I tell Mom?

- 'Cause you tell Mom everything.

- No, I don't.

- Let me see it.

- No, it's not finished.

- It's okay. It's cool.

- That's scary.

- You think?

- Thank you for seeing us at such late notice.

- We both felt that it was time for us to come in and discuss...

- What I think is going on with your son?

- Yes.

[...]