“Mean Girls,” the musical, opened on Broadway last season and it attempts to find a sweet spot between the era of the movie and the present. “The biggest difference between then and now is the advent of social media,” Fey says. “I didn’t want any of that to take over because I feel the story is about female human behavior at its core. We were lucky because of many of those fashions from the films had already come back around, so we were able to evoke the movie and the 1990s without making it feel like a period piece. We’re true to the movie, but not literally in the 1990s.”