Remember that great scene in Titanic where all the extras were running around while high on PCP-spiked clam chowder? No, oh, that's because it happened behind the scenes of the film, but even so, it's still an incredible story that you might never know about just watching the film.
This great All That Is Interesting slideshow (I know, you have to flip through all of the slides -it's not my choice but the information is entertaining) has all kinds of similar, horrible stories from behind the scenes of huge Hollywood films.