I explained the mission to everyone. We would get on the 6 train at the start of the line at Brooklyn Bridge and the twins would sit on either side of the car, directly across from their sibling. Once in place, their job would be to mirror each other as closely as possible. If one scratches his head, so should the other. If anyone asked them what was going on, they should claim not to notice anything unusual and not to even be able to see their sibling.