1. Make a note of Bill Pullman's hair-style during the movie. You'll notice that he has it gelled up.

2. Find the scene in which he has come back from the dog fight and is walking down that long walkway in Area 51's entrance. His hair is all scruffy from wearing the helmet.

3. In the shot directly after this he turns to face someone (this shot is over the this person's shoulder). We see his hair is fantastically neat again.