Oops! Dakota Johnson found herself so caught up in a round of Jimmy Fallon's Acting Game on The Tonight Show on Wednesday, January 20, that she dropped the F-bomb without even meaning to!

The Fifty Shades of Grey star was a guest on Fallon’s late-night talk show and took the opportunity to introduce her show host to a new game.

"It's called the Acting Game, and I played it once with my family and some friends," she revealed to Fallon, who, despite being the king of silly celebrity games, was keen to learn more.

"Basically you get a fake scenario, and you have to act out the scenario," she said.

Fallon was eager and quickly gave the 26-year-old actress her first scenario.

"Your fiancé, Darth Vader, is calling to tell you he's leaving you for another woman," Fallon told her.

Instantly jumping into character, Johnson played along. Unfortunately a little more eagerly than anyone was expecting!

"Hang up the phone, hang up the phone," demanded Fallon, overwhelmed by Johnson's mistaken use of the F-word. "It's an adult game," he concluded.

Watch the funny accident (and the duo's impressive improv skills) in the clip above.  

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