Simply because Yoona has dropped her solo song which came as a surprise to everyone, even the insider for SM Entertainment, hehe. I dont know why but the inspiration just floated into my mind that easily. I think only a goofball like Yuri would be able to match up with Yoona in this situation. If you havent already checked it out, here are 2 links to listen it from!http://tvcast.naver.com/v/782454https://www.youtube.com/watch?v=-h661KwBeqc (not official)