I've always wondered about this. Supposedly, Antipholus and Dromio of Syracuse have come to Ephesus specifically to search for their missing twin brothers. They're here BECAUSE they think their IDENTICAL TWIN BROTHERS might be here. As soon as they arrive, people start acting like they recognize them even though they've never been there before, and treating them like they've lived here all their lives, and not once does it occur to either of them to think, "Hmm, it's almost as if they all know someone else - someone with my face, who has a slave/master with my slave/master's face, and who have the same names as we do, exactly as you would expect to happen if our twin brothers, whom we are HERE TO LOOK FOR, were actually here." No, their explanation is magic.