January Jones goes commando on 'Tonight Show'

Mad Men actress January Jones made it very clear she wasn't wearing any underwear during her Friday night appearance on The Tonight Show with Jimmy Fallon by wearing a revealing, lacy black jumpsuit.

The head-to-toe jumpsuit was largely modest except for lacy panels along the side that showed plenty of skin and not a lot of something else that should've been there … her underwear.

While on the show, the 36-year-old actress told a mean story of how she pranked her ex-boyfriend from high school -- who's now a realtor -- into thinking she was planning to purchase a $1 to $2 million home from him.

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