On the 8th anniversary episode of KBS "Happy Together Season 3" Park Myung Soo asked fellow guest Shin Dong Yup if he ever underwent botox treatment in which he answered, "I did" causing laughter in the set.

Dong Yup answered further saying, "I just gained a little weight, also I asked Lee Hyori to get botox once", to this Lee Hyori replied, "I refused. I said no because Im a celebrity and it's normal to show people that I age. A lot of celebrities look younger than their actual age, Me however, Im just normal".

And then she was asked if she ever tried getting botox treatment in the past and she answered, "In the past, I tried it only one but it only made my eyes look weird".

Source