Louis C.K. is out. Rob Lowe is coming. And Adam Scott is signed for the long haul.

As it's improved significantly throughout its second season, Parks and Recreation has also been tinkering with its cast. First, C.K. came aboard as a love interest for Leslie, but his time on the show is over.

More recently, it was announced that Lowe will leave Brothers & Sisters this spring and recur on this NBC sitcom. We can also now confirm that Scott has been cast as a new series regular.

The Party Down star - whose resume also includes Knocked Up and Six Feet Under - is moving to Pawnee, Indiana full-time.

He'll debut this May and be included in the cast next season. Variety reports that Scott will play Leslie's new (seemingly long-term) boyfriend.

"Adam is one of the funniest and most versatile performers around," said executive producer Michael Schur. "When we designed the character he is going to play, we used him as the dream scenario of who we could get."

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.