I have a related question, to those who do count sheep. Do you count sheep walking, single file, through a gate. Or perhaps jumping, again single file, over a broken wall. Or do you imagine a big field of sheep and try and count them all??
Nobody really counts sheep, or I don't believe they do....but the idea of them jumping over a fence seems to be central to the allusion. So like I said, jokingly, I wake up when a billy goat jumps over.
From wikipedia:
"In most depictions of the activity, the practitioner envisions an endless series of identical white sheep jumping over a fence, while counting them as they do so. The idea, presumably, is to induce boredom while occupying the mind with something simple, repetitive, and rhythmic, all of which are known to help humans sleep.
Although the practice is largely a stereotype, and rarely used as a solution for insomnia, it has been so commonly referenced by cartoons, comic strips, and other mass media, that it has become deeply engrained into popular culture's notion of sleep. The term "counting sheep" has entered the English language as an idiomatic term for insomnia. Sheep themselves have become associated with sleep, or lack thereof."