Two years ago, Joo Woo Jae was criticized by several netizens for "rudely" behaving on MBC's 'Radio Star'. It was claimed that Joo Woo Jae was inattentive when fellow guest Kim Bo Sung was talking and kept on staring blankly. 

On the April 4 airing of MBC's 'Radio Star', Joo Woo Jae made his second guest appearance and mentioned the previous controversy. He playfully commented, "I'm not that popular so the behavior controversy wasn't even that big", and explained that he was looking at the monitor in the studio when Kim Bo Sung was talking. 

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He also apologized, stating, "I was bad back then. I'm sorry" and said, "I couldn't watch the episode. I saw my facial expression and had to turn off the TV right away."