The latest happening from the pranksters at Improv Everywhere – masters at getting weird looks from people as they plug in big desktop computers at Starbucks, flood Abercrombie & Fitch with shirtless average Joes, and (the best) freeze in Grand Central – is all about twins. Organizers recruited nine sets of identical twins in matching outfits to ride the 6 train uptown, sit across from each other and mirror each other's gestures. It's not The......