From the Wikipedia page for the episode:
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In the last scene of the episode where Cartman is getting a ride from the trucker, Cartman is dressed exactly like Sylvester Stallone's character Rambo in the movie "First Blood" with the trademark green Army jacket, red undershirt, and brown traveling bag. This also refers to the way he is hitchhiking and the words he speaks at the end "When a man has been wronged, he no longer cares about danger." and "You go through life being told there's justice, then you learn the only real justice...is the justice you take.
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http://en.wikipedia.org/wiki/Imaginationland
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