My Cable Co had an HBO preview last weekend. I marathoned S1 and S2 of Thrones.
I didn’t even notice the GWB head. I recall several on spikes, but none, other than the main character who got beheaded, was showing that close or distinctive.
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Since HBO is going to this extensive of an effort, apparently the inclusion was intended to be GWB’s head.
Thus, the inclusion was not done in a vacuum. It had to be designed, created, propped, and videoed. That would indicate that several people would need to have been involved.
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Much ado about over-sensitivity by some immature people involved in the development and production of the scene.
George R. R. Martin (the author of the books) was rabidly anti-Bush. I wouldn’t be surprised if it was his idea of a joke.