New York’s Grand Central Terminal is an ideal spot for a flash mob–remember when Moncler Grenoble’s stone-faced model-dancers took to the floor in Carlo Mollino-inspired skiwear? As part of the big 100th birthday bash, the insta-happening experts at Improv Everywhere recruited 135 LED-flashlight-wielding performers to light up Grand Central’s grand windows, mesmerizing passersby. The impressively choreographed affair, a project cooked up with MTA Arts for Transit, was something of a homecoming for Improv Everywhere, which in 2007 staged “Frozen Grand Central,” a flash freeze that has racked up 32 million views on YouTube. Watch both successful “missions” below.