Allison Williams has spent three seasons refusing to grow up as Marnie Michaels on "Girls," and now she'll have the chance to do it live on NBC -- as a boy.

Williams has just been cast in the highly coveted titular role in NBC's "Peter Pan Live," the follow-up to 2013's "The Sound of Music Live!" with Carrie Underwood. NBC announced the news with a tweet on July 30, saying, "Dreams do come true! #Girls star Allison Williams will play Peter Pan in #PeterPanLive!"

It certainly should be a dream come true for Williams -- whose father anchors "NBC Nightly News" on the peacock -- but it's something her character on "Girls" would literally kill for, given the struggles she's had launching her music career:

UPDATE: Williams herself expressed her joy later in the morning with an adorable throwback Instagram photo, captioned "Thrilled to be playing Peter Pan live on NBC in December. I've been rehearsing for a REALLY long time."

"Peter Pan Live" will air on Dec. 4.