The University of Pennsylvania has the least distinctive identity of any prestigious college in America. It has a robust Greek scene, but nothing compared to a state school. It has risen impressively in the U.S. News rankings—from nineteenth place in 1988 to eighth in the latest round—but it remains a second-tier Ivy, and many students have a chip on their shoulder. (When a team of psychologists asked a group of Penn students to free-associate about their school, 30 percent mentioned the phrase “Ivy League”; only 7 percent of Harvard students did the same.) Even its name is cruelly generic: Until recently, Penn’s official bookstore sold t-shirts with the motto, “Not Penn State.” If anything defines the school, it is the influence of finance: Penn sends more seniors straight to Wall Street than any other U.S. college, and it has more billionaire undergraduate alumni than Harvard.

One label Penn has latched onto is “the social ivy.” Any student—even an official tour guide—will tell you the campus has a “work hard, play hard” mentality, and in September, Playboy conferred on Penn a surprising new title: Number One Party School in America. “UPenn puts other Ivies to shame with its union of brains, brewskies and bros,” claims Playboy, whose annual party-school ranking has traditionally favored less tweedy schools, like the University of Miami. Could the Playboy honor finally give Penn the identity it never quite possessed? On Halloween—which happened to fall on Homecoming weekend—I went to investigate.

It’s just after midnight, and a sexy nurse, Kanye West, and a guy wrapped in an Italian flag are scrambling upstairs at a frat house on Spruce Street. Boys inside the party text the girls hovering outside: “Give up—the cops are here.” A frat bro dressed as Aladdin switches on the lights.

The group I’m tagging along with migrates to the house’s backyard. A few minutes later, a brother appears, looking relieved. “They gave, like, ten citations,” he says. Philly is cracking down on open containers, but the party can go on—for now. The lights are switched off. The music entreats students to put their hands up. Dixie cups of vodka and Solo cups of PBR are passed around again. Two bros clap beers, splashing on everyone around them.

Twenty minutes later, the police are back—and the brothers, nervous now, are serious about kicking everyone out. This time, we comply. “Cops busting parties is very normal,” says a sophomore from New York. “The solution is to hide upstairs, or go to another party.” We choose the latter option, and trek to another frat house down the street. We arrive to find that this party, too, has been shut down. Unfazed, my guide confers with her friends, weighing which parties might still be going. It’s about 12:30.