It happened. Mary-Kate and Ashley Olsen actually smiled in public. The sisters attended the CFDA Awards this week, and showed some rare emotions while accepting their award for accessory designers of the year. Watch the video above to see the twins grinning from ear to ear.

Mary-Kate and Ashley are known for their serious faces on the red carpet — but there is a good explanation as to why the the 31-year-olds might not want to smile in public. According to Mary-Kate, they get scared and anxious in front of the cameras, and even squeeze each other's hands to calm each other down. "We have this little thing, you know, where we love each other and we'll squeeze each other three times, and then I'll squeeze her hand back like four times, like, 'I love you too,'"Mary-Kate explained.

The Olsen twins shot to popularity thanks to their role as Michelle Tanner on Full House — and became pop culture icons at a very young age. However, fame is never something the sisters sought out. "I look at old photos of me, and I don't feel connected to them at all. I would never wish my upbringing on anyone," Mary-Kate told Marie Claire. Their younger sister Elizabeth Olsen even admitted seeing the media scrutiny Mary-Kate and Ashley experienced caused her to quit acting and focus on her schooling.

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"[My sisters'] fame made me more determined to study," Elizabeth said. "I knew I wanted to be an actor, but I also didn't want to start working when I was under 18." However, there is one place where Mary-Kate and Ashley let loose and that's NBA games. The sisters can often be seen cheering on their favorite basketball teams with huge smiles on their faces.

So, fans can expect more "prune" poses on the red carpet until further notice.