I've read complaints that Inception's dreams are pretty unimaginative scenarios, but Cobb explains that if you twist landscapes to the limits of imagination, you risk tipping off your mark. Undercover cops look and act the part.
Experiment Idea: Compile all of Inception's rules. Find someone who has not seen the film. Ask him or her to study the rules. Show him or her a version of Inception with all the talky exposition cut out. See how he or she reacts.