A: Don't I know you?
B: Your face certainly rings a bell. ("You look familiar. I think I have seen you before." or "I think we have met.")
A: "Yours too," ("You also look familiar. I recognize you too.") "you look different though" ("You look familiar, but you have changed since I saw you last.")
Maybe A + B knew each other when they were children. Now they are grown up. They look different but they still remember each other a little.