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Jennifer Garner and Ben Affleck attend Vanity Fair Oscars party after celebrating son's 4th birthday


UPDATED FEBRUARY 5, 2019 7:48 AM EST

It’s a smallworld — especially in Hollywood. Jennifer Garner and ex-husband Ben Affleck stepped out separately on Sunday evening toattend the same Vanity Fair Oscars after-party.

The 43-year-old stunned in a black Atelier Versace gown as she walked the carpet alone.Meanwhile Ben looked dapper in a navy suit at the star-studded party.

Photos: Getty Images

Following the 2016 Academy Awards, the Superman v.Batman actor also made an appearance on Jimmy Kimmel Live: After the Oscars’Special, where he sneaked best pal Matt Damon on to the show.

The Martian starwas tucked under Ben’s clothing in an over-sized suit, before host Jimmy Kimmelopened the jacket to investigate what was happening underneath. For those whodon’t watch the late show, Jimmy and Matt have a long-running “feud” with each other.

Ben told Jimmy,“ I just think it’s gone on long enough.” He added, “I think it’s maybe time tobury the hatchet here, man.”

“Thisis illegal what you’re doing. This is trespassing. This is potentially breakingand entering. You know I could have you arrested right now for this,” Jimmytold Matt. “I was actuallynominated for an Oscar and I can’t get on the Oscar show?” Matt, who lost Best Actor to Leonardo DiCaprio, said as he wasdragged off stage by Jimmy’s stage personnel.

Photo: ABC/Randy Holmes

Oncethe trespasser was removed from the premises, Ben dished on his son SamuelAffleck’s fourth birthday. Ben and Jennifer’s youngest child celebrated hisbirthday on Saturday with a superhero-themedparty and naturally when your father is Batman, it’s only fitting to ask him to dress up for the occasion.

"I was like okay. I had to callthe studio and say, 'Is there any chance someone has the costume around?'"Ben said. Though he admitted the studio was initially hesitant to loan him the suit.He laughed, "They trust me for the movie, but not for a four-year-old'sbirthday.”

Ben added that at the party, "There was Wonder Woman, Captain America, Iron Man andthere was me. It was so mortifying ... I didn't think that all the kids'parents would be there. It's 11 in the morning and [the parents] are like, wow,Batman!"

Prior to Sundays Oscar party, the actor and his ex-wife Jenniferreunited to celebrate their son’s birthday together. In a revealing Vanity Fair interview, the mom-of-three admitted that since their announcement to divorce last summer, “I need to move with the big picturealways on my mind, and the kids first and foremost.”

Photo: Patrick Demarchelier

Calling Ben, “the love of my life,”Jennifer revealed that since her divorce, she’s turned to comediennes Tina Feyand Amy Poehler. “When I can’t sleep—and I am not someonewho typically has that problem, but I really have in the last year—and I needsomething to switch my brain off, it has been Tina Fey and Amy Poehler,” shetold the magazine. “God bless those girls. I used to think I would never watchtelevision on my phone, but there I am, because I am sleeping next to mydaughter [Violet].”

While their marriage did not last,Jennifer confessed that if she had to do it all over again she would stillmarry Ben. “I didn’t marry the big fat movie star; I married him,” shesaid. “And I would go back and remake that decision. I ran down the beach tohim, and I would again.”

WATCH BEN AFFLECK SNEAK MATT DAMON ON TO JIMMY KIMMEL LIVE!