ah, i once worked on a website and photoshopped one eye of a customer for a testimonial shut. then i switched the images out for a few ms on a random timer: i.e

ah, i once worked on a website and photoshopped one eye of a customer for a testimonial shut. then i switched the images out for a few ms on a random timer: i.e., die testimonal was winking at you. it was tiny and only happened once every few minutes but led to a lot of amusement in the dev team (you mostly saw some movement in the corner of your eye, took them ages to pinpoint it down). removed it before going live, tho.