Those merry pranksters of Improv Everywhere, the architects of the performance piece “Frozen Railroad,” which saw everyone stand still in Grand Central for several minutes, have again chosen mass transit to stage one of their oddball exhibitions.

“Human Mirror” sees ten sets of twins in matching outfits board the 6 train, take their position across from each other, and mirror the other’s actions (or inactions, in the case of the sleeping twins.)