Last time we saw Mary-Kate Olsen, she was hoppin' mad - but it looks like she eventually regained her composure!

In fact, when we spotted the starlet over at the MGM building yesterday, we were stunned to see her laughing and making goofy faces with a friend before heading over to the Chateau Marmont. We were honestly a little befuddled at the sight - until we saw Mary-Kate's twin sister Ashley arriving to join the party for lunch. After all, seeing your sister's always a great reason to smile!