Hi Nikita. Arrival is great movie! Ian's answer here is a joke, not to be taken seriously. He means that the thing all twelve sites have in common is that a song by the singer Sheena Easton was very, very popular there once. It's a joke because he knows that's not the thing they all have in common. It's a funny way of expressing that he has no idea why the aliens landed where they did or what the landing sites have in common other than they are where the aliens landed. Hope that helps!