The unexpected guest has arrived.

Dakota Johnson, draped in an alluring lingerie ensemble, teamed up with Lily Allen for a surprise cameo on “Saturday Night Live,” embodying the role of the mistress named “Madeline.”

The “Fifty Shades of Grey” star captivated audiences in an ethereal, sheer lacy teddy from Bode priced at $900, paired with a shimmering sequined duster coat. Mostly obscured by a screen, Johnson complemented Allen’s performance as she crooned her latest single, “Madeline,” centered on the theme of infidelity.

Johnson delivered the spoken word segment of the track, during which Allen’s character mentions that she and her partner had an understanding to keep their affairs under wraps, urging discretion rather than openness in their betrayals.

“I hate that you’re in so much pain right now. I really don’t wanna be the cause of any upset,” Johnson expressed, moving away from the bed to join Allen.

“He told me that you were aware this was going on and that he had your full consent. If he’s lying about that, then please let me know. Because I have my own feelings about dishonesty,” she added.

“Lies are not something that I wanna get caught up in. You can reach out to me any time, by the way. If you need any more details, or you just need to vent, or anything. Love and light, Madeline.”

The “Madame Web” star, 36, then gave Allen, 40, a kiss on the cheek.

On the song “Madeline,” Allen sang about her estranged husband, David Harbour, breaking the rules in their “open” marriage.

The other woman was later revealed to be Natalie Tippett, a costume designer who met the “Stranger Things” actor, 50, while filming a movie in New Orleans in 2021.

For Halloween, Allen took a jab at Harbour by dressing up as the character Madeline from the beloved children’s book series.

In February, news broke that Allen, who married Harbour in 2020, and the actor were ending their marriage.

Allen filed for divorce in September.