I’ll let writer/director Rian Johnson take this one:
This is a strange curiosity I thought might be interesting – just after I finished the script for Looper but before we began preproduction I asked Joe to record some voice-over, and with help from my friend Ronen Verbit constructed this “fake trailer” using clips from other movies. This is a fairly common thing to do when you’re trying to get a movie off the ground, but it was the first time I tried it. It was meant to show more some of the film’s tone, and to show how the odd concept could be presented in a clear and compelling way in the marketing. Zach Johnson did the sketches. Note that we hadn’t begun the casting process yet, and the clips were chosen just based on their visuals and not by who is in them.