The question arose when CL revealed that Oh Hyuk didn't respond to her text message wishing him a happy birthday. 

SEE ALSO: Fans speculate Yeri may be leaving SM after heartfelt message to fans

Then the MCs asked Oh Hyuk, "So how should the text messages read, for you to respond back?"

Oh Hyuk was then thrown off guard when the MCs suddenly said, "If CL and IU both sent you text messages simultaneously, which one would you reply to first?"

Examples were also shown of CL's message reading '...Sleeping?' and IU's message saying, 'Are you awake???'

However, the singer failed to say anything as he sat down sweating bullets instead.  

The MCs cleverly added, "Okay fine so what if IU sent another message, 'Hey, so...'" which led Oh Hyuk to swiftly choose IU, causing much laughter.