David Cronenburg's sci-fi classic contains a lesson we should all heed: flies and humans don't mix. When a fly sneaks inside Seth Brundle's teleportation device, strange side-effects occur. Before long, those effects have morphed into full-blown mutation. As anyone who's seen Cronenburg's 1986 masterpiece will attest, The Fly will haunt your dreams. Watch it again and prepare to have your skin crawl.