Cal's lived a life. And Luke wants to know about it, especially since he wasn't able to share it. He wants to understand what Cal's lived and how he's lived it and who he's lived it with, because it all matters.

And it is a joke. And a little bit of a dirty suggestion. He still has his left hand splayed on Cal's back, holding them together. "Artoo's often told me that he's glad he can't smell biological stink with the places we end up going. But he also doesn't know the joy of getting clean with someone else."