🚀 go-pugleaf

The "cloning" part is just a copy of the movie or another movie, nothing special there. The tough part is weaving the movies together seamlessly. for that you either need very good planning, a set, and lighting for chromakey. Or you can rotoscope the images together using hand-drawn masks. The techniques are standard fare for After Effects and most editing systems but they're far too complicated to describe in these little posties.  

Suggest you visit your local booksellers or library to see what you can find on the topic of special effects filmmaking. Since you've stumbled into the thousands of amateur filmmaker Web sites, keep searching for keying technique discussions. All of the indies who are doing Lucas and Spielberg homages are heavily into keying and rotoscoping, capably producing spectacular effects sequences that are dirt cheap.  The secret to good effects is planning beforfe you even THINK about shooting. 

david