Thanks to a rush of diehard Muggle moviegoers, Harry Potter and the Half-Blood Prince has surpassed Hollywood's midnight-ticket box-office record. The sixth Potter film grossed $22.2 million in midnight sales at 3,003 locations, according to Warner Bros., slashing the mark set last year by The Dark Knight. But the record-breaking is just getting started. Unlike the last two Potter films, the new one is rated PG, instead of PG-13, positioning it to draw an even broader audience. (The first three movies also were rated PG.) Half-Blood is expected to gross more in the U.S. than the previous film—and as of Wednesday evening, it stood a chance of surpassing the record set by Transformers: Revenge of the Fallen for the biggest single day at the box office ever.