That clip was not done very well, at least not as far as the cloning techniques anyways. You can often see the join quite clearly.

The normal way of doing this is to film your talent on a blue or green screen, then just dump as many layers as your wqant over your background in your compositing tool of choice. However, in that movie they didn't use a bluescreen (at least not always) and it shows. They filmed the same actor on different occasions and spliced them together. Trouble with this is that even making the next take five minuteslater the lighting will likely have changed and you'll see the join.

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