• Ashley Olsen, joining beau Justin Bartha on the Las Vegas set of his new movie, The Hangover as

it filmed on the roof of Caesars Palace. “She was cute, laughing and

giggling throughout,” a source says. “She was wearing a headset and

listening to the whole production while Justin was shooting.” Between

takes, the two interacted, and Bartha would touch her face tenderly.

According to the source, he referred to Olsen as his “girlfriend.” While in

Sin City, the two stayed in a suite in the Augustus Tower at Caesars Palace,

and Olsen relaxed in the spa while Bartha continued filming.

• Ellen DeGeneres and wife Portia de Rossi,

joining a small group for a celebratory dinner on the patio of West

Hollywood’s Il Sole. “They’re so in love,” an onlooker tells us. “Doting Ellen

was seen feeding Portia a bite of tiramisu for dessert.” Nearby,

Kate Bosworth shared a girls night out with a friend,

splitting the Dover sole and bellinis.

• New Hollywood lounge Bardot opened its doors to friends for a low-key evening of old school tunes spun by Ryan Gosling and

a live band and burlesque show. The actor, looking dapper in black pants and

a white button-down shirt, played tunes from an elevated deejay booth while

guests enjoyed small plates of American bistro-styled food. A casual Catherine Keener chatted with friends near her table, while Brothers %26 Sisters‘ Emily VanCamp sipped wine over dinner with a

pal. Gosling seemed confident with his deejay gig, and later checked out the

live band in the neighboring room. The night ended with more tunes from

Gosling, including ’80s favorites like “Walk Like an Egyptian.”

• Vince Vaughn had the perfect dinner date while

visiting his hometown of Chicago - his mother! The actor stepped out to

Gibson’s Steakhouse for a meal with his mom while in town to support the

Chicago Cubs.

• How I Met Your Mother’s Alyson Hannigan and

hubby Alexis Denisof, sharing lunch at casual eatery Blue Plate in

Santa Monica. The two sat by the window, talking over lunch. “They kept to

themselves and were quiet,” says an onlooker. After they paid, the pair

walked out holding hands and smiling and headed down trendy Montana Avenue.

• By JENNIFER GARCIA, MARK GRAY, MARY MARGARET and LESLEY

MESSER

Celebrity Hot Spots.

Tuesday’s Caught in the Act >

Source:www.People.com

• Joel Madden, rocking 6-month-old daughter Harlow to sleep

in his arms while waiting to board his flight back to L.A. from Dallas with

Nicole Richie. “Nicole was smiling and literally skipped

over to Joel, and he handed Harlow to her,” says an onlooker. “They looked like an adorable family.” When it was time to take

off, the happy family - plus a younger, tattooed guy and an older

blonde female companion - took their seats in first class.

“The baby was wide eyed, watching everyone walk onto the plane,” the

onlooker tells us.

• Matt Damon, grabbing some Mexican food at

Paquito’s Mexican Restaurant in Aventura, Fla. The actor, who sported a

trucker hat and sunglasses on top of his head, dined with his wife and their

daughter. According to an eyewitness, Damon fed their

daughter Isabella, 2, and laughed with her as she sat in her highchair.

• Also in Miami: Ben Affleck and pregnant wife

Jennifer Garner, dining alfresco at the

Mandarin Oriental. The twosome enjoyed salads on the terrace of the hotel’s

Café Sambal, right on the Biscayne Bay.

• Dolly Parton, singing to a star-studded crowd during her

outdoor show at L.A.’s Greek Theatre. Vince Vaughnchatted closely with a beautiful brunette before the concert, and later, at

intermission, held court as fans and friends gathered to talk to him near

his table. But when she was singing, Parton had the crowd entertained:

Katherine Heigl and Josh Kelleyclapped and sang along from their seats, about 10 rows from the stage.

Nearby, Rose McGowan, in a yellow frock, stood up to clap and dance

along too. Even Jackass star Johnny Knoxville showed his

Parton fandom. He was spotted checking out Dolly tees and talking animatedly

to concertgoers.

• Eva Mendes, letting down her convertible top and

cranking up her stereo for a spin in her sleek, black Mercedes. “She was

driving, top down, hair flowing, music playing,” an observer tells us. “She

just looked relaxed, and happy.”

Also Spotted …

• Alexis Bledel, laughing while checking out Home Delivery: Fabricating the Modern Dwelling, the new exhibition at New York’s Museum of

Modern Art. … Terrence Howard and Leasi Andrews,

cuddling in a corner booth at Melrose Bar and Grill while sharing chopped

chicken salad and pita bread.

• By REAGAN ALEXANDER, PAUL CHI, JENNIFER GARCIA, MAUREEN

HARRINGTON, MARLA LEHNER and DEBI SPRINGER

Celebrity Hot Spots.

Monday’s Couples Watch >

They’re back: Jennifer Aniston and Vince Vaughn were spotted this week in Chicago in more than just a friendly embrace.

On Tuesday night, the pair were seen dancing, eyes locked, before kissing and making out as bodyguards shooed the crowd away, PEOPLE reports in its upcoming issue.

Earlier in the evening Aniston, 36, showed up at the Vic Theatre, where Vaughn, 35, brought his Wild West Comedy Show tour. During the performance, Aniston watched from the balcony. (She also caught his show Sept. 16 in Oxnard, Calif., after they filmed the comedy The Break Up this summer.) Her favorite part: when Vaughn showed an old clip of himself performing in an ABC After School Special about sex.

At the party after the show, Vaughn grabbed Aniston around the waist, pulled her to his side and told a few friends, “She’s the best!” while rubbing her back. He later gave her a kiss on the temple, and the two proceeded to make out.

In the past, Aniston and Vaughn have brushed aside rumors that they were a couple. Yet, at the wrap party for The Break Up, this summer, after mingling and dancing the two made their way to a private booth and, in the words of one onlooker, “got very cozy with each other. Very friendly and very, very comfortable with each other. The hand on the leg, the arm on the shoulder.”

At the time, Aniston’s rep denied a romance between the two, telling PEOPLE, “Do not read into this. At the wrap party . . . everyone was enjoying themselves, cast and crew included, and they were all being very affectionate to each other.”

Aniston, meanwhile, has declared herself ready to date again, telling Oprah Winfrey that she is open to whatever comes her way. “I love the unknown. I love the discovery of what will be happening and just kind of sitting back and not knowing,” she said last month.

Aniston’s divorce from Brad Pitt was finalized on Oct. 2.

More on this story

• Jennifer Aniston: Birthday Quiz!

• Heidi Montag, color-coordinating her baseball

outfit with Spencer Pratt while watching the Los Angeles

Dodgers beat the Cincinnati Reds. The Hills star didn’t seem

too invested in the game, however, chatting instead with her fiancé and neighbors in the stands. Also on Heidi’s mind: getting photographed. During the seventh inning stretch, she and Pratt stood up - not to sing, but to pose for pics. Days earlier, Montag also got noticed while taking her camera crew for a full body wax at Ona Spa in Los Angeles (she was filming her MTV hit). Montag was wearing a white sundress which, a source says, was (oops), “totally see-through!”

• Also at the Dodgers Game: Nick Lachey, getting

booed when the jumbotron showed the Cincinnati native waving a Reds cap. The

crowd of 35,000 began yelling while he simply smiled.

• At Rihanna and Kanye West’s

Hartford, Conn. show, Chris Brown was spotted grooving from the side of the stage and enthusiastically cheering on his girlfriend, “as if he was seeing

%26#91;her%26#93; for the first time,” a witness tells us.

• Renée Zellweger,

grabbing a quick bite at the Palm in West Hollywood en route to the airport.

The actress ordered salmon, which was brought out immediately, and had a

glass of white wine while doing some business on the phone.

• Kelly Clarkson, beating the unseasonable heat

with some Chardonnay at Asia de Cuba at the Mondrian Hotel in West

Hollywood. The pop star dined with friends and ate a noodle box and chicken

skewers.

• Vince Vaughn and buddy Tom Morello (of

the bands Rage Against the Machine and Audioslave), sharing dinner, a show, then breakfast in West Hollywood. After dining at the Rainbow Room, the guys ventured next door to Key Club to see the band Steel Panther - the band formerly known as Metal Skool - perform. An onlooker tells us that the guys and the ladies they were with were “totally rocking out at a table.” Following the musical mayhem, the group went to an IHOP in Santa Monica,

eating breakfast food and chatting for over an hour.

Also Spotted…

• Brody Jenner, club-hopping around Chicago -and taking an extended stop at the Underground. … And Matthew Fox and Zach Braff, munching on some Buffalo chicken wraps at Crown Bar in West Hollywood.

• By REAGAN ALEXANDER, JENNIFER GARCIA, MAUREEN HARRINGTON,

LESLEY MESSER, EUNICE OH and MICHELLE TAN

Celebrity Hot Spots.

Tuesday’s Caught in the Act >

Jennifer Aniston and John Mayer are taking their relationship in a new direction - south of the border.

Last Friday, the couple - who first stepped out in public in April - headed for a little R%26R at Casa Aramara, the sprawling beachfront home of Girls Gone Wild mogul Joe Francis, in Punta Mita, Mexico.

The house is a hot spot for celebs: Demi Moore celebrated her 45th birthday there in November, and Aniston has visited the pad with former beau (and costar) Vince Vaughn and platonic pal Orlando Bloom.

“Jen spent time laying out on the loungers on the patio. John was always around, standing by her, making sure she was comfortable,” says an onlooker.

Before departing for Mexico, Aniston and Mayer were also spotted discreetly holding hands June 12 while double dating with Aniston’s BFF and former Friends costar Courteney Cox and her husband David Arquette.

• Reporting by JENNIFER GARCIA

• Jennifer Aniston and John Mayer, looking “besotted with one another” while enjoying a late-night rendezvous with friends - including actor Billy Crudup - at the Chateau Marmont hotel in West Hollywood, a source tells us. Nestled at an outside courtyard table, the two sat close as Mayer talked feverishly with the group and Aniston indulged in one cigarette after another. But their focus was definitely on one another: “John and Jen were giving each other longing looks and were practically sitting on one another,” says the source. After an hour, they left Crudup and company behind and headed home together.

• Vince Vaughn, signing baseballs for young fans in the stands at L.A.’s Dodger Stadium. “Vince was chatting and joking around with them and leaning in close so he could get their names right,” says an onlooker. The actor, who hung out with a male friend, cheered on his hometown team, the Chicago Cubs, as they beat the Dodgers 3-1. Also at the game: Chris O’Donnell, who sat a few rows behind home plate with several of his children, You Don’t Mess with the Zohan star Emmanuelle Chriqui, who threw out the first pitch, and Justine Bateman.

• Nicole Kidman and Keith Urban, laughing and whispering into each other’s ears during a screening of Adam Sandler’s Zohan comedy at the Green Hills Cinema in Nashville. Ever the gentleman, the singer picked up snacks - popcorn, soda and water - for him and his expectant wife before the movie started.

• Robert Downey Jr., holding court with his entourage of 10 pals (including comedian Richard Lewis) at Hollywood lounge Green Door. The Iron Man star, dressed casually in jeans and a T-shirt with a suit coat, relaxed with his posse in the secluded Library Room as they waited to see the venue’s new live rock night, Lo Hi Fi. “He was super-friendly to people,” says a fellow reveler. Also making the scene: Prince, who arrived with an entourage of attractive dark-haired women. The night before, the singer celebrated his 50th birthday (on June 7) with a low-key evening at Teddy’s at the Hollywood Roosevelt Hotel. Far from a big b-day blowout, he had drinks with a tall brunette companion in a slinky black dress and another couple at a table near the deejay booth.

• Diddy, dancing shoulder to shoulder with R%26B singer (and rumored girlfriend) Cassie at a birthday party for rapper Busta Rhymes at New York City club Marquee.

• By EILEEN FINAN, JENNIFER GARCIA, MARY MARGARET, LESLEY MESSER and MICHELLE WARD

Celebrity Hot Spots.

Monday’s Couples Watch >

Age: 28
Hometown: St. Thomas, Ontario
Current gig: Playing Owen Wilson’s love interest in the comedy Wedding Crashers

She’s never been an uninvited guest
Although she’s starring in a movie about two lotharios (Wilson and Vince Vaughn) who sneak into weddings to pick up women, McAdams has never crashed a wedding. “We thought about it when we were shooting,” she tells PEOPLE. “We were out in Maryland staying at this beautiful hotel and there was a wedding on the grounds. We were kind of jealous and we thought, ‘You know, we could say it was research.’ But we chickened out.”

So what about her own wedding dreams? The actress, who doesn’t discuss her dating life, will probably forgo the Vera Wang gown and lavish reception. “I would rather keep it quiet and cheap,” she says. “I’d rather spend the money on the honeymoon.”

She was almost a star on ice
McAdams first laced up her skates when she was 4, and the years she spent as a competitive figure skater have worked in her favor as an actress. “Doing a sport totally helps you,” she said recently. “It’s great for your work ethic, and I love doing physical work as an actor because I’ve really become in tune with my body.”

Acting was also an early passion. “I wanted to get into it as a little kid and my parents were like, ‘Maybe later,’” she says. “A theater company came to town and I begged my mom to let me do it and then I started there.” After high school, she enrolled in the theater program at Toronto’s York University, and acting gigs, including a role in the 2002 comedy The Hot Chick, followed soon after graduation.

She’s the queen of the double bill
Her real breakthrough was last year’s one-two punch of the teen comedy Mean Girls and the romantic tearjerker The Notebook. “(Those movies) were so different, and I got to show some range,” she says. “It’s the combination that helps me to be considered for all different kinds of movies.”

This summer, she’s again pulling double duty: After Wedding Crashers, she’ll star in the Wes Craven-directed thriller Red Eye, due Aug. 19. The movie, in which she plays an airplane passenger abducted by Batman Begins’s Cillian Murphy, was particularly claustrophobic to shoot. “When I first got on there I was like, ‘I’m going to go insane. I’m going to go insane,’ ” she says. “(But) after a month I was like sitting on the plane, buckling up, getting ready to get terrorized and it was all in a day’s work.”

She likes to escape the spotlight
Even though she took home the MTV Movie Award for breakthrough female in June, McAdams has no desire to live in the limelight like her Mean Girls costar, Lindsay Lohan. To stay grounded, she’s avoided moving to L.A. “Toronto is home and it suits me,” says McAdams, who’s still tight with parents Lance and Sandy and siblings Kayleen and Daniel. “It’s good to step away from the business when I’m not working and ride my bike and garden. It just keeps me centered.”

As his Marley %26 Me costar Jennifer Aniston was seen enjoying mealtimes with John Mayer in Miami, Owen Wilson’s weekend found him socializing with Richie Sambora as well as with his Wedding Crashers costar, Vince Vaughn.

Late Friday night at Nobu at the Shore Club - looking “a little disheveled and withdrawn from everyone,” a source tells PEOPLE - Wilson dined with a group of buddies before making his way to the Florida Room at Delano, where he met up with an unlikely pal: Sambora.

Meanwhile, Dylan McDermott was just one table away, and eventually joined the two others in their discussion. “They were just being guys, hanging out, friends talking,” says the source.

By Saturday, Vaughn had flown into town and joined Wilson for a bit of fun on South Beach, a source tells PEOPLE,

“They hung out at Casa Tua until 5:30 a.m.,” says the source. “The restaurant usually closes by 1 a.m., but they kept it open late for Owen and Vince.”

As for what took place, “The guys hosted a private party inside and had a blast,” the source added.

Though they’ve been apart romantically for more than a year, Vince Vaughn is still known as Jennifer Aniston’s ex - and that’s fine with him.

“I have such a great friendship with Jennifer,” the host of Vince Vaughn’s Wild West Show, 37, tells this Sunday’s edition of Parade magazine. “Really, I still talk to her constantly. I have a real, genuine connection with Jen. And I have a real appreciation of her. That continues to this day.”

“I always try to keep my relationships quiet and my work at the forefront,” Vaughn says.

“I haven’t been someone to go and talk about those things, because that’s not what I want to be known for,” he adds. “In regular life, people date, and sometimes it works out, and sometimes it doesn’t. We get more attention because we’re more known.”

Women Like the Big Kid

Vaughn also says his perceived immaturity - like his 2005 Wedding Crashers costar, Owen Wilson, he’s known as a big kid - hasn’t affected his relationships.

“I’ve been fortunate that the women I’ve dated seriously get used to it, because I think I’m attentive and aware in other ways,” Vaughn says.

“It hasn’t hurt my relationships. It’s not a big deal,” he says. “With relationships, for me, the biggest foundation always is that you can laugh with each other, that you have fun with each other, because life really is made up of all the little moments. Of course, I also got better at communicating.”

Vince Vaughn hopes to put the “ho ho ho” back into the holidays with his new movie Fred Claus - in which he plays the older, overlooked brother of the big man in the red suit (Paul Giamatti as Santa). It opens Nov. 9. At a press conference for the comedy, a very unScrooge-like Vaughn, 37, talked of Christmases past, present and future.

What is your secret Christmas wish?
I guess, understanding. As a kid, Christmas is fun because you want toys. Then when you get socks or shirts you kind of don’t want those. As you get older that is all you get. It’s nice to have kids around, because you kind of get to enjoy Christmas. I have a nephew and some nieces and them opening presents and being excited in that way is fun.

Do you remember when your belief in Santa was first shaken? (SPOILER ALERT: Do not read if you still believe in Santa Claus.)
I remember the day I had neighbors that let me know - I was 6 years old - that there was no Santa Claus. They go, ‘You know there’s not a Santa Claus, right?’ - and, of course, covering in front of them I was like, ‘Well, yeah. Of course there’s not a Santa Claus, guys.’ Then I went to my sisters, and they said, ‘Okay, now you know the painful truth, there is not a Santa Claus.’ I was the youngest. They said, ‘Don’t tell mom and dad, because then we may not get gifts anymore. You got to keep pretending that you think there is Santa Claus, or you are not going to get any gifts.’ I was like 16 going, ‘Dad, when is Santa coming down the chimney?’ My dad was like, ‘Look it’s getting weird, you are getting older, you know there’s not a Santa, right?’ ”

What would it take to restore your belief in Santa?
Funny how that works. We just did this fun short %26#91;film%26#93; for the World Series with these kids. We did Claus kind of coaching. We did the whole thing and it was over, one of the kids was 9 or 10, came running up to me afterwards. He goes, ‘Hey, Fred.’ I felt like Joe Green in that Coca-Cola commercial. He’s like, ‘Hey, Fred.’ I turned and looked at him, I said, ‘Yeah.’ He says, ‘Tell your brother to get me something this year.’ I looked at him and I said, ‘Oh, I got you. I got you.’ So, now I’m just hoping that this guy is getting something good. Otherwise he’s going to hunt me down.”

Naughty or nice … which were you?
I would have been naughty, but in a very nice way.