Jason Segel might not be one to kiss and tell, but judging from his interview with Extra yesterday, he's completely smitten with new love Michelle Williams! In an interview with Extra yesterday, Jason's face just lit up the moment he heard her name mentioned. Plus, his Five-Year Engagement co-star and good friend Emily Blunt shared her own thoughts on his lovestruck transformation!

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When Extra's Michael Yo asked Jason about his relationship with Michelle, Jason smiled hugely and said, "I think I would just verymuch like to be happy. That's all I have to say about it." But the way he looked saying it tells us all we need to know -- he's got it bad!

And then Emily added, clearly totally excited for her friend, "He's a man-boy! He used to be aboy-boy and now he's a man-boy!" To which Jason replied, "I think I might evenbe becoming a man-man... potentially!" When a guy is willing to "grow up" for a girl -- and genuinely seems excited about it -- that's when you know he's really in love. The fact that he taped photos of Michelle, with the words "I Love You" surround them, to the back of his phone is a pretty good clue, as well!

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Jason went on to talk about writing the role of his fiancée in The Five-Year Engagement for his friend Emily, saying, "You want it to feel organic and you want it to feel likeyou're actually friends on screen. Emily was my friend and she's like the best actress in the world." The best actress in the world... except, of course, for your Oscar-nominated girlfriend, right, Jason? That's totally what you meant to say, don't worry, we won't tell Michelle.

Do you think Jason should write a role for Michelle next, or should they keep their relationship and work lives separate?

Video courtesy of Extra