Celebrities appearing in TV commercials is nothing new, but celebrities making fun of themselves in the name of civic pride, well, THAT doesn’t happen every day. But welcome to the edgy new “I Love New York” ad campaign, unveiled Thursday at City Hall with many of the good-natured stars themselves on hand, including Barbara Walters, Woody Allen and Mayor Rudolph Giuliani. The new commercials are seen as a way to help boost tourism since a dramatic drop in visitor arrivals to the Big Apple since the Sept. 11 attacks. Working with the ad agency BBDO, the city premiered its “Miracle of New York” public service ads, showing that anything can happen in the city, such as Barbara Walters trying out for a Broadway musical (she can’t sing — at all). Other “miracles”: Yogi Berra conducting the New York Philharmonic (and asking at the end, “Who’s Phil Harmonic?”), Woody Allen executing a perfect leap on the ice at Rockefeller (yeah, sure), Henry Kissinger running the bases at Yankee Stadium and sliding into homeplate (then asking, “Derek Who?”), Billy Crystal and Robert DeNiro preparing for Thanksgiving (the former as a turkey and the latter as a pilgrim). And possibly the best of all: A woman in the Stage Deli, where sandwiches are named after stars, asking the waiter for a Ben Stiller, with Bacon. From the back of the place appear Ben Stiller and Kevin Bacon. The woman then asks for a doggie bag.