At one of IU's small-theater concerts, Akdong Musician took part as special guests. Although the siblings were known to be big fans of IU, this was their very first time meeting her.

Although Akdong Musician were clearly nervous, that did not stop them from showing their playful side! When IU said she was very pretty, Soo Hyun responded by saying that IU was very thin, creating a friendly atmosphere.

After the two performed "200%", IU said, "You guys are so good. I'm going to go crazy from how refreshing it is."

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The siblings said, "When we were in Mongolia, we danced along to [IU's] 'Boo'.  We are really IU fans."

Chan Hyuk said, "This is the first time we appeared as guests at someone else's concert, and the response was good, so I'm thrilled. I should tell the CEO that I want to do a concert soon." Excited, he danced to their song "Artificial Grass", but fell during his performance. Although taken aback, he stood right back up and finished their performance safely.