NEW YORK -- President Obama reminisced with a group of Brooklyn high school students Friday about his days living in the hip borough. He told them, yes, Brooklyn was "cool" even then, back in his college days.

"But not this cool," he said to laughter. "Barclays Center hadn’t been built yet.  I know the Nets just picked up Paul Pierce and Kevin Garnett off season, which is a lesson to all the young people -- old people can still play.  We’ve still got some gas in the tank."

So, after the public event, Obama hung out down the street at Junior's, famed for its cheesecake. Yes, he has an affection for dessert that he often mentions, something that does not endear him to his health-conscious wife. But the real reason for the unscheduled stop was to add a little presidential glamor to the mayoral campaign of Bill de Blasio, New York City's elected public advocate whom polls show leading the race to succeed Mayor Michael Bloomberg (I).

"Do you know your next mayor here?" Obama asked the stunned diners as he entered. Then he proceeded to order two cheesecakes -- one plain and one strawberry -- that he told the waitress he would be eating, with others, on Air Force One back to Washington.

Obama hugged some patrons, signed a pumpkin sitting on the restaurant counter, and asked a girl about her day at school. Then headed back to Marine One, parked in Prospect Park, for a quick twilight flight into Manhattan to raise money for the Democratic Congressional Campaign Committee and the national party.

There the president attended a reception at the Upper East side home of Kathryn and Kenneth Chenault, chairman and chief executive of American Express. About 60 donors paid $16,200 a person to be there, and the funds go to the Democratic Congressional Campaign Committee. Obama then attended a private fund-raising at the home of Karen Mehiel, a prominent Democratic donor.

The final fundraiser of the evening was held at the Upper West Side home of Beth and David Shaw, a writer and a hedge fund manager, respectively.