Jason Segel, Michelle Williams Affectionate, Inseparable at First Public Event as Couple

Jason Segel, Michelle Williams Jeff Vespa/WireImage

Jason Segel and Michelle Williams are taking their romance from the streets of NYC to red carpet events!

On Wednesday in NYC, the actor celebrated the premiere of his new flick The Five Year Engagement and was joined by his new girlfriend at the film's after party, where an eyewitness tells Us Weekly he looked completely "on top of the world."

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"Michelle didn't do the red carpet but wanted to be there for Jason's big night," the observer tells Us. "She snuck in to sit in the theater during the screening, then they all went over to the after party together where they were hanging out with his co-star Emily Blunt and Robert De Niro."

"Michelle was really sweet but her usual shy self in crowds — she stayed close to Jason and only really engaged in conversation with people that she knew," the eyewitness adds. "Jason would put his arms around her waist and they gave each other a few sweet pecks — they definitely seemed to have a physical chemistry."

Marveled the onlooker: "Every actor in there was so enamored by the couple!"

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After they were spotted on several occasions around the Big Apple together, the 32-year-old actor finally broke his silence on his new unexpected relationship with Williams, whose famous ex is the late Heath Ledger — the father of her 6-year-old daughter, Matilda.

"I think we would just very much like to be happy. That's all I'm going to say about it," the actor said on an episode of Extra earlier this week.

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A few days beforehand, he was spotted holding his iPhone with pictures of Williams, 31, taped on the back. The phrase "I love you" was written around the photos.

Segel — who has been linked to Michelle Trachtenberg and Linda Cardellini in the past — is the perfect person for Williams, a pal told Us. "Jason has already shown her his commitment to her."

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