You sure it's a birthmark, man? 'Cause sometimes that Nam grass will do weird things to your face, too, you know.
9 seconds sound clip from the Cheech and Chong's Up in Smoke movie soundboard.
You can hear this line at 00:24:44 in the Blu-ray version of the movie.
Quote context
[...]
- Whatever you do, don't say nothing about his birthmark there, man, because he flips out.
- Hey, I ain't going to talk about nobody's birthmark.
- Yeah, don't look at it, either.
- Come on.
- No, I'm Pedro, man. Open up.
- I don't know. Somebody's messing around in there, man.
[...]