A birthday party full of seven-year-old children, sent off to watch Megamind — a cute, PG movie that's apparently all about blue people — instead ended up watching the opening minutes of Saw 3D. Apparently, a few scenes were shown before the mistake was recognized — scenes that included a man getting his foot cut off and a woman being killed with a buzz saw.
In other words, one of the more upsetting things I can imagine happening to me — a full-grown person with an (I think pretty reasonable) aversion to torture porn. Parents of the children are, understandably, pretty pissed about the nightmare-ridden traumatized youngsters they're left with.
The movie theater, in a gracious apology, gave everyone free tickets for a different movie.