The character of Shoshanna wasn't supposed to be recurring, but creator Lena Dunham liked Zosia Mamet's performance so much that kept her on the show as a regular, because they saw potential for exploring the character thanks to Mamet's talent.
Jemima Kirke had to be convinced by Lena Dunham to take the role of Jessa, because Kirke didn't (and doesn't) have a long-term interest in acting, compared to her focus on her thriving career as a painter and artist.
The celebrity connections of actors and members of the creative team of Girls (2012) continue to expand: the cast includes the daughters of David Mamet, Brian Williams and Simon Kirke, the composer is Sean Penn's brother and three episodes have been directed by the son of publisher Martin Peretz. In addition, actress Audrey Gelman, who's been featured in two episodes, is a former press aide to Hillary Clinton who now serves as the press officer for Manhattan's Borough President.
On July 14, 2016, Peter MacNicol (who plays Jeff Kane on the TV series Veep) was Emmy-nominated in the outstanding guest actor in a comedy series category. However, less than a week later, a Hollywood Reporter article reported that his nomination was rescinded when the Academy of Television and Arts and Sciences, the body that awards the Emmys, determined that MacNicol had appeared on too many episodes in one season (5 out of a total of 10) to be considered eligible as a guest. The Academy's qualification for "guest" status rests on having appeared in fewer than 50% of a season's total episodes; MacNichol appeared in only about 10 seconds of that fifth episode, but he was still disqualified. The Academy also specified that the new nominee would be the actor who originally won the next-highest number of votes without actually being nominated. Several days after MacNichol's disqualification, that actor turned out to be Peter Scolari, who was nominated for playing Tad Horvath on Girls. On September 10, 2016, Peter Scolari actually won that Emmy.
Amy Schumer auditioned for the role of Shoshanna. Lena Dunham says: "Everyone in the room was stunned by the detail and skill of her improv, the wild talent radiating off her (and I was personally intrigued by her breasts). It was clear Amy wasn't meant to play an innocent Juicy Couture lover obsessed with emoji - even if her Meatpacking District club lingo was the funniest shit I had ever heard. But when she left the room, the vibe was very 'Someone give that lady a show, STAT!'"
Dakota Johnson auditioned for this show. Unfortunately, didn't get the part but got offered to audition for 5-Year Engagement by Judd Apatow. Later, becoming widely known through her talents in Fifty Shades of Grey, Black Mass and many more.
Despite being credited for Season 4 Episode 4 "Cubbies" Andrew Rannells does not actually appear in the episode. This is the only time in the series, thus far, that an actor is credited for an episode they are not in.
The trivia item below may give away important plot points.
Christopher Abbott (Charlie) left the show before the third season started filming because of creative differences with creator Lena Dunham, resulting in the relationship of Charlie and Marnie ending abruptly off-screen between the second and third season.