It's an old joke, but it has to be mentioned on such a thread:
Intense girl is grilling the boy the entire date. On the way home, she continues her farher.
"Tell me," she asks. "What's the difference between din and yashrus?"
He thinks for a second and then answers.
"Mi'tzad hadin, I should drop you off right here. Yashrus is that I drive you home."