One, inevitably, is the double vision: two sets of eyes, often from two identical faces, staring out at the world together.

ECONOMIST: Double vision

Now we were going along a multilane highway, with other cars alongside us, and I kept my eyes staring straight ahead, fearing the laughter and crude comments that the sight of the two of us was no doubt prompting in the cars around us.

NEWYORKER: The Daughters of the Moon