Emmy Rossum backstage at the Conan show. Credit: Emmy Rossum/Instagram

Tres chic! Normally demure Emmy Rossum showed off her silly, saucy side in the moments leading up to her appearance on Conan on Monday, Jan. 28.

The Beautiful Creatures actress went for an old-Hollywood vibe with a navy-and-white polka-dotted Stop Staring! dress and red pumps for the interview, and promoted her appearance on the talk show in a series of posts on her Instagram.

In one, the 26-year-old actress peeps coyly over her shoulder from her dressing room, showing off plenty of leg as she lounges in a director's chair. In another, the Shameless starlet points her rear end at the camera as she leans into the mirror.

"Very excited to go hang out with my buddy @ConanOBrien tonight," she tweeted Monday afternoon. "He's my favorite ginger."

PHOTOS: 25 most stylish New Yorkers

During her stop on the late-night show, Rossum sang for a pastrami sandwich and had a cat sound competition with the host while promoting her new album, Sentimental Journey, out Wednesday, Jan. 30. 

This isn't the first time Rossum has worked to shed her pristine image. In an interview with Manhattan magazine earlier this month, the actress explained how she had to convince the Shameless producers to let her audition for the role.

"They didn't want to see me; they wouldn't even [let me] audition," she told the magazine. "They thought my image too glamorous, that I couldn't not be pretty."