As a celebrity, there may be no easier way to reach your fanbase than on Twitter. Want proof? Look no further than Chrissy Teigen, who uses the platform to do everything from shut down haters to crowd-source bruised bananas for baking banana bread. This week, Teigen had an IRL interaction with another vocal Tweeter, Chloë Grace Moretz—who famously once feuded with Kim Kardashian over 140 characters—at an event for Forevermark. Moretz has recently been quiet on Twitter, meaning the duo had plenty to catch up on in person. Also this week, Mary-Kate Olsen made not one, but two appearances alongside husband Olivier Sarkozy (and sister Ashley, of course), and teen-beloved pop star Austin Mahone—not to be confused with equally teen-beloved pop star Shawn Mendes—kicked off the holiday season, performing at Fossil's festive dinner. Here, a look at the best party pictures of the week.