The reason the joke is funny* is that it insinuates that Sarah Palin has no control over her underaged children.... which we all know is kinda true. It's actually more of a slam against Sarah and her parenting skills than those poor kids of hers.
* to some of us
Please, you can turn on Maury or Springer to see that this issue is happening all over the country. I think Palin's kids are a walk in the park compared to some of the shit that's been stinking up our tv screens.
BTW, Letterman hasn't been funny since the 80's.
















