Hyoyeon confessed that she was the most popular when she was a trainee.

YoonA, Yuri, Tiffany, and Hyoyeon were guests on 'Happy Together 3' that aired on January 17th. During the show, Hyoyeon was asked, "When was your best time period?". She answered, "I don't know if I had one. I was popular only when I was a trainee."

YoonA confirmed, "Hyoyeon was the celebrity of all the trainees. She had fans even when she was a trainee".

Hyoyeon continued, "I debuted after going through a long training period, but I wasn't as popular as I was when I was a trainee. I told myself there was nothing wrong with my abilities." She was then asked, "What do you think was the problem?", and Hyoyeon gestured to her face, causing everyone to laugh.

Source: Osen