Barack Obama’s critics say it’s what you don’t know about him that matters. With a little help from talk-show host David Letterman, the senator is opening up.

Presenting “Top 10 Surprising Facts About Barack Obama,” the Democratic candidate listed his first act if elected president: “Stop the fighting between Lauren and Heidi on ‘The Hills.’”

In an appearance on CBS’s “The Late Show” taped for broadcast Thursday night, Obama also admitted that in the Illinois primary he “accidentally voted for Kucinich.”

“When I tell my kids to clean their room,” he said, “I finish with, ‘I’m Barack Obama and I approved this message.’”

And this: “I have canceled all my appearances the day the ‘Sex and the City’ movie opens.”

The No. 1 surprising fact about Obama? “I have not slept since October.”