I went to a youth group at the age of seven. One of the leaders, in a vindictive mood, confided to all of us that the other leader had a glass eye - and if we snuck up behind her and hit her in the back of the head, it would fall out.

He also told us not to tell her we knew about the glass eye, because she was extremely sensitive about it. The fact that she would be uspet by us mentioning her glass eye, but not by hordes of children punching her in the back of the head seemed perfectly reasonable to us.

She didn't have a glass eye, of course. So it never fell out. We tried for ages to get that damn eye out.