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.
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 However, less than a week later, a Hollywood Reporter article reported that his nomination was rescinded when the Academy of Television and Arts and Sciences, the body that awards the Emmys, determined that MacNicol had appeared on too many episodes in one season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.
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.
Ironically, despite playing the most care-free character in the cast, Jemima Kirke was in real-life the only one of the"girls" to be married at the time of filming the first season, and had given birth to her first child only three weeks before the shoot.
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.
The trivia items 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.
During season 6, while Desi and Marnie are in the process of getting divorced, Desi briefly dates Tandice Moncrief, played by Lisa Bonet. A February 2016 piece in Vulture revealed that there was a sequence deleted from the season 5 premiere that would have provided the names of Desi's 7 ex-fiancées, and one of those women was supposed to have been the actress Zoë Kravitz. In their real lives, Lisa Bonet and Zoë Kravitz are mother and daughter.
In a February 2017 interview with Vulture, Ebon Moss-Bachrach (who plays Desi) said that the revelation late in the run of the series that Desi has been addicted to Oxycontin the whole time he's been a character on the show was as much of a surprise to him (Moss-Bachrach) as it was to the character of Marnie and to the viewers. Moss-Bachrach also said that he found it difficult to balance the surprise revelation of Desi's drug addiction (a subject that he sees as inherently serious) with the comic requirements of the episode.