since ryeowook and sungmin had activities to do, they left "kiss the radio" for 5 day and Dana (the grace) and Key (Shinne) replaced them.

while the radio was on air, they called sungmin and ryeowook to see how they are doing and sungmin had a short talk. he was supposed to pass the phone to ryeowook, but kyuhyun took the phone and pretend to be ryeowook.

actually, it sounded just like ryeowook. dara and Key were fooled for a few seconds, but then they found out that he is not ryeowook. after that, he passes it to yesung and it was ovious that he is not ryeowook, so at the end they passed it to ryeowook kekeke

check it out here:

http://www.youtube.com/watch?v=NxG2ZUTPB7s&feature=related