Katy Perry's demo of 'Passengers' before Britney Spears recorded it leaked online

Katy Perry witnessed a song she wrote with Sia and produced by her ex who is not great at sex, Diplo, get the Britney Spears treatment.

Now we can finally hear Perry's original demo of "Passengers," which appeared on 2013's Britney Jean.

Here's Katy's version:

And here's Britney's version:

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