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Watch Scarlett Johansson Trap Jimmy Fallon Inside A Box Of Lies

Natasha and Gumby, sitting in a tree...

So, you want to catch Scarlett Johansson in a lie? You might want to reconsider that thought; as the Black Widow, the "Avengers: Age of Ultron" star knows a thing or two about spinning a web of lies.

Johansson appeared opposite Jimmy Fallon on The Tonight Show last night, competing in an intense game of Box of Lies. The rules are simple: Open up a box, and either tell the truth or lie about the contents inside, with no one but you and the audience knowing the full picture. It's then up to your rival to determine whether you're being honest or coming up with complete nonsense off the top of your head.

For instance, if your box contains a Black Widow action figure sitting on a park bench with Gumby, it's your prerogative to lie and say that you're actually in possession of a hot dog bun shaped like the Hulk. The ruse might not work, but hey, depends on how you sell it.

Watch Johansson and Fallon's battle of the fibs for yourself:

Johansson has plenty of other lies to tell this weekend, as Natasha Romanoff returns in "Age of Ultron," out now.