Sienna Miller & Jimmy Fallon Can't Stop Laughing During 'Tonight Show's Lip Flip!

Sienna Miller can’t hold back her laughter while making an appearance on The Tonight Show Starring Jimmy Fallon on Wednesday (February 7) in New York City.

The 36-year-old actress expressed an interest in interviewing herself, so she and host Jimmy swap mouths in a super hilarious round of “Lip Flip” and end up duetting Nancy Sinatra‘s “These Boots Are Made for Walkin’.”

PHOTOS: Check out the latest pics of Sienna Miller

Sienna also discusses how she ended up competing against Olympic bronze medalist Chemmy Alcott in a ski race, her work with International Medical Corps in Nigeria and filming her play Cat on a Hot Tin Roof for movie theaters.

Click inside to watch the rest of Sienna Miller’s appearance on The Tonight Show…