On the April 17 broadcast of JTBC's 'Knowing Brothers', ASTRO members Cha Eun Woo and Moonbin appeared as guests alongside announcers Lee Hye Sung and Jang Ye Won!

When it was his turn to quiz the 'Knowing Brothers' members about himself, Cha Eun Woo asked, "I have a secret that happened to me recently. What is it?" The idol also shared a hint to make the guessing easier, saying, "It has something to do with the fancam version videos that are uploaded on YouTube. We all filmed a fancam version performance, but of the 6 members, only my fancam was not uploaded."

The 'Knowing Brothers' member to answer the question correctly was Kim Young Chul! He guessed, "When you got dressed for the stage, you forgot to zip up your pants." Cha Eun Woo exclaimed, "Correct!"

The idol went on to recall the situation by explaining, "We filmed the fancam version about 4 times. Or 5 times? But it wasn't until the 5th time that I realized that my zipper was open." The other 'Knowing Brothers' members then joked, "It was Moonbin who did it!"

Cha Eun Woo wrapped up by saying, "The color of the underwear I was wearing that day didn't help either so... We have a lot of moves where we raise up our arms so that our shirts are pulled up, and my underwear kept saying hello every time. So that fancam can never be uploaded."