After Vader has lopped off Luke`s hand. Luke is hanging onto this weather vane type thing. Vader starts giving him the bad news about his parentage, and tries to turn him to the dark side.

The scene switches from Luke doing his best chipmunk face to Vader holding out his hand in an endearing manner. Well, if you watch closely, you can see Vader`s helmet jiggling about in the wind.Obviously didnt have his toupe tape on that day!