You can use this Sandbox to try out things with the Amara tool.

The video that is primarily streaming here is http://www.youtube.com/watch?v=ZU2kyr9jRkg , which is completely blank. But you can go to the URLs tab to add the URL of another video and make it primary.

Please remember to download your subtitles if you want to keep them, as they will get deleted - and the streaming URL reverted to the blank video if you changed it - after a week or two,