Nothing better than an adapted joke, especially one that's adapted to poke fun at Dubyuh.
This started out as a rude gag, but works ok in this fashion too:
George Dubyuh was definitely the dummy of the Bush family. His dad, President George Herbert Walker Bush, was at one time the head of the CIA - a mean, mean man. He used to train his guard dogs intensely. They wouldn't move a muscle until he said the command word, "Liberty". He placed delicious raw liver in bowls and said to the dogs "eat!!" They remained still, even though they twitched, slavered and drooled.
He said "Eat liberty!" and the dogs lunged and wolfed down the meat.
"Gee, that's impressive" said Dubyuh.
Bush Snr says "Do you want to have a go?"
Dubyuh says "ok, but can I just have cornflakes?"