Go to the part where Coopers ballet for the student workshop are practicing their dance. When Cooper and Charlie are kind of "competing" over what dance moves to do, Cooper did one dance move then Charlie tries to make it better. after a few, Cooper has no sweat when the camera goes to Charlie and back to Cooper, sweat is all over his shirt, When before only a little bit was there. I'm a dancer and yes you do sweat a lot, but after one dance move sweat doesn't cover your body through your shirt, not like that.