Defconn became the butt of a joke when his fellow '1 Night 2 Days' members couldn't figure out what his real name was!

Although they all knew his first name - Dae Joon - they couldn't figure out for the life of them what his surname was. Although there were numerous guesses - Kim Dae Joon, Jung Dae Joon, even Jae Gal Dae Joon - no one could figure it out! "You all only search for your own names," Defconn said, disappointed.

It turned out that Defconn's surname was actually Yoo! The members were surprised at this turn of events, and an annoyed Kim Joo Hyuk said, "What kind of a name is Defconn, anyway?"

It probably doesn't help that he's often called 'Coni' on his show, 'Weekly Idol'!