When The Rock smashes out the taillight on the Porsche, it was a mistake - he wasn't actually supposed to do that to the real car which was on loan to the set. After smashing it in, the director and crew were completely silent. The Rock said, "I wasn't supposed to do that, was I?"...silence..."Did we just buy this car?" There was a slight pause as the director checked with someone on the set... "Yes."
http://imdb.com/title/tt0351977/trivia