It was a Philadelphia phenomenon: This summer, two of cinema's biggest stars, Harrison Ford and Gary Oldman, were left largely undisturbed as locals instead cozied up to their Paranoia costar: the unusually fan-friendly Liam Hemsworth - and his visiting fiancee, pop princess Miley Cyrus.

The cast is back in town, at least until this week. And the lovely young couple are again embracing Philly and getting chummy with, really, anyone who wants to get chummy.

Hemsworth was barely back to work last week when three freshmen La Salle University speech pathology majors heard he was around the corner at Rogues Gallery and ditched their class trip at the Mütter Museum to gawk.

In frigid temps, Kaylie McNally, Megan Leonard, and Kelsey Yaiser waited patiently outside the bar for Hemsworth, discussing his cuteness factor and how they would make worthier partners than his current choice.

Eventually Hemsworth, after several long hours of filming, exited the bar, and rather than head to his waiting car, approached the shivering girls to say hello - and went into his immediate pose mode, wrapping his long arms around all three girls.

"He was just cool," McNally said.

The couple's fans gathered and were rewarded during the summer, too. Cyrus and Hemsworth chatted and posed with the devotees when they regularly visited the Starbucks near their digs at the St. James. When Hemsworth and Richard Dreyfuss (another Paranoia star) met Mayor Nutter at Bardascino Park at 10th and Carpenter, onlookers got a cheery earful from Cyrus, who gabbed like a neighborhood gal out for a stroll. On her own, Cyrus shopped at Urban Outfitters, Dr. Martens, and Philly AIDS Thrift; recorded at Milkboy Studio on North Seventh; visited Old City's historic district; and dropped into the Elfreth's Alley home of pastry chef Carolyn Santamauro to eat lemon sandwich cookies fresh from the oven.

Now, as Hemsworth returns to work on Paranoia's second round of filming, he continues to be attentive - to photo-snagging fans while filming outside Tangerine at Second and Market, during drinks at the Continental Midtown, and at El Bar in Fishtown. (Don't cross the Aussie, though: TMZ.com posted a video of him punching a guy outside that Continental party. Reports said Hemsworth thought the guy threw a rock at him.)

It's a no-brainer why Cyrus, 20, a recording star with more than 8 million Twitter followers, and Hemsworth, 22, the centerpiece of the billion-dollar film franchise The Hunger Games, are fan bait. But their accessibility is unusual for on-location actors, even the friendliest. Mel Gibson hung out at Bar Noir when he was filming Signs, and Bruce Willis (Twelve Monkeys), Denzel Washington (Philadelphia), and John Cusack (Money for Nothing) visited the after-hours nightclub Revival (now defunct) in the '90s. While those elder thespians were fine posing with fans during their time in Philly, Hemsworth - documented over and over on YouTube - goes out of his way to pose with any and all comers. In the meantime, Cyrus maintains an ongoing dialogue with her Twitterati, involving them in her life on a sometimes hour-by-hour basis. She might not give away exact locations of her travels, but she often documents them afterward.

Sharon Pinkenson, executive director of the Greater Philadelphia Film Office for 25 years, has seen stars come and go, as well as the excitement that goes with them ebb and flow.

"I truly think it has to do with the celebrity and where they are in their life and career," Pinkenson says of the pair's openness to fan interaction. The couple are hot, in their prime, and not afraid to show it. "If a person is lovely and happy and happy to be in Philadelphia, happy with their work, and doesn't feel too overwhelmed by the media and the fans, if they're outgoing anyway and not shy, which many actors are without lines to read, and if they happen to be media-savvy and looking for good press, well, then, you've got a great shot at getting their kindness and maybe even their enthusiastic attention."

Christina Kallas-Saritsoglou, cofounder of Philly AIDS Thrift with Tom Brennan, recalls her Cyrus-savvy staff rhapsodizing about Liam and Miley's first stop at the shop in August.

"It stunk that it was my day off so I only heard tales of their visit," she says of her still-giddy employees. But just as she was looking for photos of Cyrus to put up on the store's Facebook page - "Guess who was here with a new haircut" started the FB post; the do was freshly sheared, short, and platinum blond - a staffer yelled, "Miley's here again!"

With that, Kallas-Saritsoglou and company said hello, let the "beautiful and awesome" starlet shop unhampered by staff and gawkers, and invited Cyrus back to Philly AIDS Thrift offices when finished with her shopping.

"She told us there that she loved our stuffed animal tree, that she wanted to do something similar in her house and took pictures with us. She was so cute," says Kallas-Saritsoglou. "She wanted to come back to our store after that first trip because she joked about having ADD and couldn't take it all in." (The thrift store is filled wall-to-wall and floor-to-ceiling with chic vintage clothing and tchotchkes.)

Kallas-Saritsoglou, 45, thinks Cyrus related to her staff - big fans who were largely in the same age group - and felt at home. "She seemed just like a kid, totally unpretentious." Cyrus must have felt the same love: Almost immediately she posted one of their shared photos on Instagram.

Amanda Thieu, 15, has been a fan of Cyrus and Hemsworth since they costarred in the soppy 2010 flick The Last Song. She happened to be shopping at Urban Outfitters this summer when her friend yelled from the clothier's second-floor steps.

" 'Come up now' is what my friend shouted to me," says Thieu, a student at Science Leadership Academy. "She was a little snobby to the people standing in line in front of her but only because they stepped on her foot. Miley was cool and accommodating with me, though. Her friends tried to hurry her up but she was totally nice while we talked." The only other star that Thieu would charge up a set of steps to see - other than Hemsworth? "One Direction, definitely."

Earlier in the summer, Lizzie Vellozzi's father, Philly producer/actor/extra Sonny Vellozzi, looked forward to having his daughter visit him on the Paranoia set at the Comcast Center. It would be her first time seeing the local thespian - who has appeared in everything from The Sopranos to Invincible - doing his thing. He was proud to show off in front of his daughter. Then Liam and Miley happened.

"She's a big Hemsworth fan to begin with, so there was that, but as soon as she saw Miley, she ran over to her and the two bonded like chatty teen pals," Vellozzi says, laughing. "So much for dear old dad."

Last week, Hemsworth filmed outside Science Leadership Academy. Heading out of class, Vellozzi saw him leaving, apparently to film a scene, and this one time, he simply couldn't stop for photos.

From the looks of things, there's always tomorrow.