Phoebe Waller-Bridge’s mind can go to some seriously dirty places.

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The “Fleabag” creator and star was on “The Tonight Show” Wednesday and played a game of “Think Fast!” with host Jimmy Fallon.

The game was simple: One person asks a question, the other says the very first thing that pops into their head.

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Things got very funny very fast, with Fallon asking questions like “How old are most teenagers?” and Waller-Bridge quickly responding “Seven!”

But things truly took a turn for the blue when the host asked “Why is it so hard?” and Waller-Bridge’s answer had him blushing so hard he had to cover his face and rip up his cue cards.