I didn't believe until I saw it. The cat on this 'Lost' poster (at least I assume that's what it is!) really does turn its head to follow the guy as he walks past! Wish I could tell you more about it, like where it's from, for one thing. What I do know is that Mashable says the phenomena occurs when an image is placed on a concave surface such as the corrugated tin fence on which this poster is glued.

A similar effect happens when a picture's subject looks directly into the camera lens, like the portrait below, or almost every picture I've ever seen of Jesus.

Actual weird science.