There is a new genre of YouTube vid, the Re-Cut no doubt started by 10 things I Hate about Commandments"
People take existing movies or TV shows and re-cut a trailer that will make you want to quote Inigo Montoya.
Here is a great Mary Poppins one called "Scary Mary"
The Forrest Gump one is hilarious too. But if you want one that is topical check out Seinfeld Recut (Not Work Safe)