The scene portrayed a conversation of Yoo Si Jin and Seo Dae Young before they flew over to Urk. Seo Dae Young said, "I heard there are a lot of beautiful women in Urk. Kim Tae Hee in the fields, SISTAR in grape farms, and more.."
It turned out that Song Joong Ki actually wanted to use a different girl group name for this line. He strongly recommended using AOA, while Jin Goo wanted to use SISTAR. The argument did not end easily, which led to a competitive match of rock, paper, scissors.
Ultimately, Jin Goo took victory, and SISTAR was chosen to be placed in the line. Too bad for AOA's Seolhyun, who has been showering her ideal type Song Joong Ki with affection!
But still, maybe Song Joong Ki is also a huge fan of AOA and Seolhyun after all!