Here's a better link to the prank, and
here's a link where the guys explain how they did it.
They said that they only normally get to use 30-40% of the material they write beforehand, but they actually ran out of jokes with Palin. If you want some real laughs, read the transcript, in case you don't catch the funny little things the guys throw in that she doesn't even notice. For example:
"A: You know my wife is a popular singer and a former top model and she's so hot in bed. She even wrote a song for you.
P: Oh my goodness, I didn't know that.
A: Yes, in French it's called de rouge a levre sur un cochon, or if you prefer in English, Joe the Plumber...it's his life, Joe the Plumber."
"de rouge a levre sur un cochon" means "lipstick on a pig"