I first heard it on mynintendonews.com so I went and checked to see if it still worked on my WiiU...and it didn't. Least, not right away.
What you need to do, for any youtube video you want watch on Youtube, is use that video's embed link (exp:youtube.com/embed/__________(<----videocode)). To copy the embed link (it should already be hilighted) simply use your stylus/ finger and touch and hold on the hilighted text. I've tested this and it works. With anyluck maybe Google/ Youtube will fix their website so that it works.