07/30/2014 09:48 am ET Updated Jul 30, 2014

Allison Williams Cast As Peter Pan In NBC's 'Peter Pan Live'

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Maybe Marnie Michaels will never really grow up. NBC cast "Girls" star Allison Williams to play Peter Pan in "Peter Pan Live," which will be broadcast on Dec. 4.

"Peter Pan Live" is the network's follow-up to last year's "The Sound of Music," which starred Stephen Moyer and Carrie Underwood, and garnered 18.6 million viewers.

NBC Chairman Robert Greenblatt had previously suggested that the network would cast a man to play Peter Pan, but clearly it went in a different direction:

UPDATE (11:30 a.m., July 30): Williams took to Instagram to share her first post ever: a throwback photo in which she's dressed up as Peter Pan. "Thrilled to be playing Peter Pan live on NBC in December. I've been rehearsing for a REALLY long time," she wrote.

Williams' vocal abilities have been highlighted on "Girls," but her character Marnie's budding music career is used as a running joke. Let's hope her rendition of "I Won't Grow Up" goes over better.