We all know that Joffrey's a bit off the deep-end mentally, but this sh*t is beyond whack. [SEASON/BOOK 1 SPOILER ALERT AHEAD]
If you keep your eyes peeled when King Joffrey takes Sansa Stark to gaze upon the spiked head of her dead father around 12 minutes in, you'll notice that one of the heads looks slightly familiar. The show creators David Benioff and D.B. Weiss, explained in their DVD commentary (from Season 1, episode 10) that the decapitated head is actually George W. Bush.
Benioff and Weiss stress that Bush's head cameo was by no means a political statement, and was used simply because "we just had to use whatever head we had lying around."
Fair enough. Though I wouldn't put it past Cersei to have lured Dubya to King's Landing under the guise of oil and/or information regarding Stannis' alleged WMD's.