Jennifer Lawrence Lied Her Face Off On The Tonight Show

Spoiler alert: It is not a miniature horse on a bed of Flintstones vitamins.

It takes some nerve to come on the Tonight Show and lie right to the face of host Jimmy Fallon, but that's exactly what Jennifer Lawrence did on Thursday — only not very well.

The actress dropped in for a round of "Box of Lies" with Jimmy: a game in which, sitting opposite each other with a windowed panel between them, the two celebs took turns removing items from a collection of mystery boxes, and then did their best to punk each other about what the contents were.

Related: Love Jennifer Lawrence? So Do Her X-Men Co-Stars

Jennifer started out strong — wisely choosing to tell the truth when she pulled a Rubik's cube encased in Jell-O out of her first box — but Jimmy came back on a technicality, convincing her that he was holding a Backstreet Boys action figure when it was actually a tiny John Stamos.

"I feel like that, if it's not the truth? You're a sociopath," Lawrence said, before guessing incorrectly.

And when the actress's Hail Mary attempt at a big lie fell flat — despite her best efforts, her opponent did not believe that she'd pulled a miniature horse on a bed of Flintstones vitamins out of the final box — it was victory for Jimmy! And for truth. Hooray.