Oh, it's youtubes close caption feature. #checked.
http://25.media.tumblr.com/tumblr_m6...r632o1_500.png
http://31.media.tumblr.com/tumblr_m6...r632o2_500.png
http://25.media.tumblr.com/tumblr_m7...r632o1_500.png
http://31.media.tumblr.com/tumblr_m7...r632o2_500.png