Raiders of the Lost Ark (1981)
Raiders of the Lost Ark includes one of the most iconic villains of the franchise: Dr. Rene Belloq, played by Raul Freeman. In one of the most classic scenes that is frequently paused, Freeman is able to deliver his lines, even despite the fact that a fly flies directly into his mouth! Talk about dedicated to the craft.
Signs (2002)
The classic alien movie Signs by M. Night Shyamalan does eventually reveal its extra terrestrial creatures. However, early on in the film, viewers can catch a very brief glimpse of one of these creatures. If paused at the right moment, you can catch a blurry alien running around, foreshadowing what will come next.