You can do this by changing the urlURL with ANYany video.
Simply take the video id (like the KqnB2Ew0SFMKqnB2Ew0SFM
above in the 1st answer
and add it after this: http://www.youtube.com/watch_popup?v=http://www.youtube.com/watch_popup?v=
(getting http://www.youtube.com/watch_popup?v=KqnB2Ew0SFMhttp://www.youtube.com/watch_popup?v=KqnB2Ew0SFM
if using that video)
This way, the video takes up your whole screen and is forced to play in HTML5 (well, just make sure you're in the HTML5 player trial to begin with, if you aren't already...you can opt-in by going to www.youtube.com/html5)
Enjoy!!