Sure you know what you're doing up there?
2 seconds sound clip from the The Wedding Singer (1998) movie soundboard.
You can hear this line at 00:56:07.723 in the Blu-ray version of the movie.
Quote context
[...]
- Well, hey, if you don't want me to, I won't do it.
- Why would I not want you to?
- Good, then I'm going out with him.
- Robbie.
- Oh, good. That guy needs to get laid.
- Jules is chums with him. She'll fix it up, won't you, Jules?
- Hey, you guys, you know what would be fun? Let's all go on a double date.
- Okay.
- Sure you know what you're doing up there?
- Yeah, well, just don't drop a dumbbell on your head.
- So you still haven't been dating anyone new, have you?
- Is it your confidence? Are you nervous about your penis?
[...]