Washington DC, Dec. 15 -- Actor Dakota Johnson made an unexpected appearance on Saturday Night Live this weekend, joining singer Lily Allen during her musical guest performance, according to People.

The latest episode of Saturday Night Live season 51 aired with Josh O'Connor as host and Lily Allen as the musical guest. During the show, Allen performed Madeline from her latest album, West End Girl, a song in which the narrator confronts a woman named Madeline who had an affair with her husband.

As Allen sang from the side of the stage, Johnson, 36, remained concealed behind a sheer curtain. Before the performance concluded, she stepped forward, revealing herself to the audience and joining Allen at centre stage.

"I hate that you're in s...