User blog comment:XD1/George W. Bush's head on a pike/@comment-5014364-20120615005931

Oh crud this is turning into something: http://io9.com/5918114/george-w-bushs-decapitated-head-appeared-on-game-of-thrones?popular=true

HBO released an official statement:

"We were deeply dismayed to see this and find it unacceptable, disrespectful and in very bad taste. We made this clear to the executive producers of the series who apologized immediately for this inadvertent careless mistake. We are sorry this happened and will have it removed from any future DVD production."

So then B&B responded:

"What happened was this: we use a lot of prosthetic body parts on the show: heads, arms, etc. We can't afford to have these all made from scratch, especially in scenes where we need a lot of them, so we rent them in bulk. After the scene was already shot, someone pointed out that one of the heads looked like George W. Bush. In the DVD commentary, we mentioned this, though we should not have. We meant no disrespect to the former President and apologize if anything we said or did suggested otherwise."

So they're actually going to edit that digitally. I honestly believe that they just grabbed whatever prosthetic props were available in bulk (logically, world leaders would make up a large portion of these).