Michelle Williams and Jason Segel in New York on March 24, 2012 Credit: Jae Donnelly/InfPhoto.com

His many weeks with Michelle!

Since Us Weekly broke news last month -- with adorable photo evidence -- of Jason Segel and Michelle Williams' unexpected new relationship, the couple has stayed quiet about their surprisingly serious relationship.

But Segel, 32, finally piped up when asked by Extra about Williams, 31.

"I think we would just very much like to be happy. That's all I'm going to say about it," the actor said alongside 5 Year Engagement costar Emily Blunt.

Blunt herself cooed of Segel's romantic evolution: "He's a man-boy! He used to be a boy-boy and now he's a man-boy."

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Joked Segel: "I think I might even be becoming a man-man... potentially!"

In all seriousness, insiders told Us that Segel "has been trying to be more of a grown-up lately" to show his "commitment" to Williams, single mom to daughter Matilda. "He is taking care of himself more, exercising, eating right and dressing better. Basically, not acting like a frat boy anymore."

Friends for years via mutual pal Busy Philips, the couple's relationship "kind of happened overnight!" another pal marveled.