Is it Bristol, Mercede, Willow or ?????

What was David Letterman thinking? He wouldn't be the first or last to get the girls mixed up. He did say "knocked up." A clear reference to Bristol.

"So did Letterman, as Keith suggests, go too far?"

"Sarah and Todd Palin React to Letterman Bashing"
Todd went too far calling it a joke about "raping his 14-year-old daughter", where's his mind?

"And is it not a comedy show, where stars are lampooned?"

Sarah said the point of her trip was to attend an Autistic charity event? She gave a 3 minute speech and participated in a walk. That was fine, but hardly the point of her trip. It was more like the point of sister Heather's trip, who gets the short end of it. Poor Heather, autism and sister are in Sarah's shadow.

Where are the Palins now? Alaska?
'Houston, we have a problem'
Why are they taking on a comedian now?

Letterman beats NBC's 'Tonight Show'

update: Zeigler and Letterman respond.
MSNBC confuses Bristol and babies 5:32 AM Thursday, June 11, 2009
6:55 AM January 11, 2009
MSNBC mixed up about Palin/Johnston babies
Discussion of David Letterman, Sarah Palin, and Bristol Palin, on Morning Joe today.
It was Judy Giuliani at Yankee Stadium with the Palins, not Bristol or Willow? What next?

The following images were all mislabeled on blogs and in the media. It is not unusual for Bristol Palin to be mistaken for others. It happens often with her sister, Willow. Unlike the ones of Mercede those images aren't as easy to find now.
mistaken identity: a Palin wedding

These images all were said to be of Bristol.