Toward the beginning of the first disguise mission, there's some Nazi activity that'll make you look twice (at least!). In the locker area after you present your papers to the Germans, you pass into a room where three Germans are playing cards. To the right of the door, look at the two windows looking out into the sub pen floor. You'll see two Germans. Press the "Use" key when you're by the window and watch the Germans demonstrate an impressive variety of dance hall skills.