An Inside Job

For some reason, I was thinking about "inside jokes" tonight. You know, those phrases that are funny and meaningful only to a select group of people in your life. Even decades after one is born, hearing it will still make you chuckle, or take you back to a time or place in an instant.

The first three from the distant past that came to mind for me were:

"What d'you think about that?"
"I can be...flexible."
"But...when will they open?"

Without setting them up for us -- just to maintain their mystique for the rest of the world -- what is the punchline or tag phrase from your favorite inside joke?