The amount of effort that goes into a crafting a movie trailer is unquestionably insane. So much rides on the public's first impression of a new film that a trailer needs to be totally on-point, playing-up the selling points while downplaying any potential negatives fans might latch onto. Almost all movies are still in active production when a trailer is released, and so it shouldn't be too surprising that sometimes plans change a little, or rather, plans change a lot. These 8 movies featured teasers and trailers which featured significant plot and aesthetic elements which were drastically overhauled during production and absent from the final product. Whether a deliberate attempt to dupe audiences or simply a desperate dash to forge the most coherent story, these trailers built up audience expectation only for the final product, whether good or bad, to deliver something else. Yes, most of them ultimately reflect negatively on the end product, remaining a hint at what could have been, but it just goes to show that even when studios are gambling with hundreds of millions of dollars, nothing is a sure thing. Here are 8 movies that changed hugely from the trailers...