Photos of Girls' Generation's YoonA falling forward in laughter have become a hot issue.

A set of photos titled "YoonA burst out in laughter during a photo shoot" were posted online. In the photos, YoonA is dressed in a long dress, seemingly talking to Jang Geun Suk. Netizens are thinking he must have said something to her because she suddenly started to laugh so hard that she had to sit down. Jang Geun Suk, who had just been smiling, couldn't help but double over with laughter as well.

What do you think made them laugh so hard?