Here is a good interview by Daniel Bryan. The whole Yes! thing was his idea that he just started to do when he turned heel.
http://www.lordsofpain.net/news/wwe/Daniel_Bryan_Talks_Yes_Changing_His_Life_Punk_Lesnar.html
http://www.lordsofpain.net/news/wwe/Daniel_Bryan_Talks_Yes_Changing_His_Life_Punk_Lesnar.html