Speaking at the Adobe Summit, he told the audience and press including Vanity Fair: "I am working on a prank that will end his career.
"If you take the time, if you're willing to sit on one for a couple of years, and just plant the seed... there's no rush."
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He added: "I got a bumper sticker in the shape of a pot plant that said 'F*** cops' and I put it on the back of his [Toyota Prius]. Because there's no way you're not getting arrested with that."
She told E! News that he was pulling off "better pranks" these days, and admitted she had been caught out on the set of Money Monster.
However, she refused to reveal exactly what it was he did, laughing: "I can't. I will later. It's a really good one."
