One of my favorite movies as a child was The Time Machine based on a book by H. G. Wells. It featured the green, meat-eating Morlocks who lived underground ruining the paradise the time traveler found in Earth's distant future.
Of course, Hollywood's idea of time travel (in The Time Machine and Back to the Future) is nothing like what scientists think could really happen. And some people claim to have traveled through time--without a machine. I researched this idea in my book How to Travel Through Time.
Here are a few stories from the book.