The "Girls" creator had been sharing a series of throwback snaps to her Instagram Stories on Friday, April 19 to illustrate the strength of her friendship with her "best friend" Jemima to celebrate the actress recently joining the photo-sharing site, and at one point she posted a screenshot showing that they once had a FaceTime call lasting almost 90 minutes.
However, she made a mistake by forgetting to blur out Jemima's number and the British-born star ended up being inundated with unsolicited calls and messages, so Lena swiftly deleted the post and then wrote a message asking her fans not to call the number.
"You guys I know I accidentally put @Jemima_Jo_Kirke's number on Instagram but plz do not call or text her she's a mom :( (sic)," she wrote in another story. "I was trying to be nice and made a huge mistake."
The 32-year-old then shared a text exchange with the actress in which Jemima asks if she remembered to take her pain medication that day.
In another screenshot from their text conversation, Lena can be seen informing Jemima that she was deleting the post and calling herself "stupid".
In the messages, Jemima tells Lena, "my phone won't stop... texting calling... relentless," and Lena replies, "I'm SO sorry... Oh my god."
Over the top of the exchange, the TV writer told fans, "I'm really an idiot, she laughed, I'm so lucky."
Lena and Jemima became friends when they were children attending Saint Ann's School in New York City.
Jemima, who has two children with estranged husband Michael Mosberg, joined Instagram earlier in April.