For the first time ever, Doctor Who is set to feature a guest star who is openly transgender.

36-year-old Bethany Black has been cast for the ninth episode of the show's ninth season, which is the second season for current star Peter Capaldi. Black's role is unknown, but she's not playing a transgender character.

She is best known for her autobiographical "Beth Becomes Her" live show, which tackles taboo topics from her own past with a darkly comedic bent. Black was also the star of an episode on British anthology series Banana, which was created by former Doctor Who showrunner Russell T. Davies. Black wrote of her personal history with Doctor Who on her Facebook page, where she also shared her joy and excitement at landing this role, which she called "the gig of a lifetime."

Black joins a ninth episode guest star lineup that includes Reece Shearsmith, Elaine Tan, Neet Mohan and Paul Courtenay. Shearsmith is well known to British audiences for co-creating and starring in sketch comedy/horror show The League of Gentlemen, alongside another name that should be very familiar to Doctor Who fans: Mark Gatiss.

Gatiss, it just so happens, is the writer behind the Who episode in which Black, Shearsmith and the others listed above appear. Shearsmith has his own history with Doctor Who, having played actor Patrick Troughton, a.k.a. the second Doctor, in the TV film An Adventure In Time and Space. (Which, incidentally, was also written by Gatiss.)

Gatiss has written several prior episodes of Doctor Who, typically bone-chilling, monster-of-the-week fare like "The Idiot's Lantern" and "The Crimson Horror." He also co-created and writes episodes for Sherlock, alongside current Doctor Who showrunner Steven Moffat, where Gatiss co-stars as Mycroft Holmes.

(Did you get all that?)

Season 9 of Doctor Who debuts on September 19, 2015.

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