She and Sulli were guests on the August 21 installment of MBC's 'Radio Star'. During one of the segments, Krystal was asked, "I heard that the Girls' Generation members forced you to watch a 19+ (similar to 'R' rating) movie", and she said, "That's true".

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She explained, "I watched the movie 'American Pie'." Rapper Defconn responded, "In America, that's nothing, it's like PoPoPo (Korean Children show) over there." The other MC's stated that the movie did contain some nudity and Krystal continued, "I went to visit the unnis, and they were watching it. It's hard to remember everyone, I remember Jessica, YoonA, Taeyeon, and Tiffany unni being there. I tried to leave because there was a sex scene but they called me back in. After I came out of the room, I was so embarrassed that I just turned my back on it. I'm underage, so it was really embarrassing".