Is your photocopier scary? Cyclops: monsters with one eye. The Graiai: monstrous sisters who all share one eye and one tooth. Singularity is monstrous, and one is the loneliest number. People like symmetry; we like seeing things in pairs of two. But the idea that there's an exact copy of ourselves out there somewhere? Most people don't like that. They find multiple births frightening: just look at the twins from ‘The Shining’ or ‘American Horror Story’. Doppelgängers frighten and fascinate us at the same time. But for every horror doppelganger, there's a cute Ditto. Which means odd and even can both be equally scary. Your digital double especially.