It's the hidden camera prank that the members and KARA's manager pulled on Han Seung Yeon!
KARA had just won the Mutizen on Inkigayo and they were moving onto their next scheduled event, KBS' The Teacher Is Coming. Han Seung Yeon was fake interviewed along with her members and the plan was to mostly ignore Seung Yeon. When Seung Yeon noticed she wasn't getting any attention from the interviewer, she answered some questions before anyone else had a chance.
Then, they took out a lie detector and asked her if she wanted to be part of Girls' Generation. She said no but the detector was set to say she was lying. She and her fellow members were brought into a state (a more genuine state for the unaware Seung Yeon) of shock. The interviewer then asked if she ever regreted becoming a KARA member and she surprisingly said "Yes." Leader Park Gyu Ri was trying to hold in her tears, but unfortunately could not and rushed immediately to the restroom. Nicole followed her and maknae JiYoung followed suite. Seung Yeon's reason for her answer was that she did not realize how much she gave up to become a singer and once she did figure it out, it was all too late.
The drama doesn't end there! They were switching filming locations and moving to another restaurant when a police officer stopped KARA's vehicle and accused their manager of drunk driving. This was all planned, but the unaware Seung Yeon grew wary since their manager had just left the five girls alone there.
When they were told to step out of the car, the police officers handcuffed all the Kara members, excluding Seung Yeon. Just when things were finally getting interesting, it was then revealed that one of the policemen was Seung Yeon's teacher from middle school! When the MC's of the show came out and all was unveiled, she started shedding tears.
Her teacher had always remembered his student that wanted to be a singer, but was very calm in class, showing a true student-teacher bond between the two. Also towards the end, Seung Yeon's tears stopped at the sight of her old friends. Reunited and it feels so good!
source : allkpop.com
