Someone who works in my boss's office only has one eye, and she wears her hair down (patchless Gabrielle-style) over the missing one, which I'd assumed was a glass eye as obviously you don't want to look too much. It was only the 3rd or 4th time I saw her that I realised it isn't a glass eye but an eye drawn onto a flesh coloured patch that's stuck over the socket. It's very unusual and not particularly well drawn either (although granted I didn't notice it at first) and of course once you see it it can't be unseen. It feels unkind to say it's creepy but, well, it is.