I had that one on tape for awhile, so I watched it about ten times, before I finally taped over it. I think I know it better than any other episode, besides the classic Christmas ones.
The Gibson-portrayal was a bit over the top...like the man himself. Some hilarious references to Gibson's previous movies, slipped in there. Such as, when Gibson screams "Give me back my money!," it's a reference to the movie "Ransom" where he yells "Give me back my son!" At one point, he yells "Freedom!," which is lifted from "Braveheart." And he keeps saying things like "Torture me all you want, I won't tell you anything," which is a reference to all the times he's been tortured in his movies, personally, and of course the torture that is the raison d'etre of "Passion."
It's been suggested that Gibson is, at heart, a clever sado-masochist. I don't know about that, but I do know from his interviews about this film that he thinks Christ's suffering and death are the most important parts of the Christian religious tradition. In his view, and in most of the early Catholic instruction I received in Catholic school until the hippie-priests and guitar-masses of the early-'70's took to the peace, love and mellow good-fellowship road, the message was always one of humankind's guilt for Jesus' suffering. As one nun memorably put it to me, "every time you do something wrong, you're hurting Jesus, and inflicting another wound." Oh, okay...I'll try not to go insane from that psychological pressure, Sister Hell.
One more movie-reference, that was pretty good, was Gibson chasing the boys' bus in a gasoline-truck, like the one he drove in "The Road Warrior."
Off the Gibson-track, the funniest part of the episode for me was when Cartman was leading his pack of followers in a rousing chant, something in German about "Killing the rotten Jews," which the "followers" took to be him speaking in Aramaic, the ancient language used in the movie. Then he says something like, "And then we will load them on the trains (but we won't talk about that in the open)." LOL!