Blake Lively and sister Robyn Lively have been having a whirlwind adventure in NYC this week. After celebrating Galentine's Day with their mum at a L'Oréal event and attending the Michael Kors runway show hand in hand for New York Fashion Week, the two were photographed walking through the city together on Wednesday. Although they looked absolutely gorgeous (as usual), what we really want to know is what had them cracking up. Did they just read one of Ryan Reynolds's hilarious tweets, perhaps? Or maybe one of the photographers made a Teen Witch joke? Either way, we can't get enough of how adorable they are.