Righteous dude!

It didn't take long for Ashton Kutcher to become the most popular guy among the cast and crew of Two and a Half Men.

PHOTOS: Check out Ashton's incredible abs

Charlie Sheen's replacement on the the smash CBS sitcom threw an impromptu "first day party " for the entire show's staff after the first day of shooting wrapped on Friday, an insider tells Us Weekly.

With wife Demi Moore at his side, the 33-year-old was a happy host in the back room of West Hollywood hotspot Troubadour, "buying drinks" for all comers, the insider says. DJing the off-the-cuff bash was Jordy Masterson, the brother of Kutcher's former That 70s Show costar Danny Masterson.

PHOTOS: Guess the age differences with these couples

Kutcher and Moore, 48, "were both cute together and friendly with everyone," the source tells Us.

Indeed, the low-key celebration epitomizes the new Zen Kutcher brings after the chaos of Sheen's ouster earlier this year.

"Everybody is loving Ashton on the set," the source raves. "He's really coming off like a cool low maintenance guy, and with everything that went down with Charlie everyone is breathing a sigh of relief."

PHOTOS: Charlie Sheen's craziest controversies

Unlike 45-year-old Sheen's drama, "He jokes with the crew, has no tantrums, he comes in well studied in his lines -- it's such a nice change. So far there have been no issues and everyone is really happy with how it's working out."

Adds the source: "Nobody is missing Charlie right now."

Get more Us! Follow us on Twitter, Friend us on Facebook, Subscribe to Us Weekly