From http://en.wikipedia.org/wiki/NUMMI#History
This is the funniest thing I've ever heard in the auto industry - any one ever find a coke bottle in their door?The choice of the Fremont plant and its workers was unusual. At the time of its closure, the Fremont employees were considered "the worst workforce in the automobile industry in the United States", according to the United Auto Workers. Employees drank alcohol on the job, were frequently absent (enough so that the production line couldn't be started), and even committed petty acts of sabotage such as putting "Coke bottles inside the door panels, so they'd rattle and annoy the customer." In spite of the history and reputation, when NUMMI reopened the factory for production in 1984, most of the troublesome GM workforce was rehired, with some sent to Japan to learn the Toyota Production System. Workers who made the transition identified the emphasis on quality and teamwork by Toyota management as what motivated a change in work ethic.