The Oscar-nominated actress' monologue was also crashed by her husband, Mumford & Sons frontman Marcus Mumford.
Carey Mulligan made her Saturday Night Live debut this weekend and charmed the audience with her fun opening monologue. The Promising Young Woman star made her SNL debut, and kicked things off by poking fun at her famous similarity to another Oscar-nominated actress.
"People in America are always saying the nicest things to me, like, 'I loved you in Brokeback Mountain' or 'You were amazing in Fosse/Verdon,'" Mulligan shared. "And I used to say, 'Oh, sorry, that's Michelle Williams.'"
"But now, I just say, 'Thank you! I am Michelle Williams," Mulligan added with a broad smile.
She also said how excited she was to host the show after her husband, Marcus Mumford of Mumford & Sons, had been a musical guest on the show three times before.
"He couldn't be here tonight, so he's at home watching the children. So, hi, Babe! Love you!" Mulligan exclaimed, only to be surprised by her husband standing up in the back of the audience.
"What a surprise! Lovely to see you. Where are the kids?" Mulligan asked.
"I left them with the Sons! Couldn't miss this for the world. You're going to smash it. Really, SNL! This is amazing," Mumford exclaims. "Just be sure to soak it in because after it's over, you're going to think about it. All the time."
Mumford then asked the question he really wanted to know: "Do you know if they booked a musical guest for tonight?... If they're needing anyone, I'm happy to do it."
As it turns out, her husband even brought his acoustic guitar, just in case. And he joined her on stage so that he could play her an outro for her monologue.
Check out the video below to see more highlights from this season of the celebrated sketch comedy series.
Saturday Night Live airs live, coast-to-coast at 11:30 p.m. ET, 8:30 p.m. PT on NBC.