Jimmy Kimmel might never take a vacation again.

While the late-night host was away, he had science-themed YouTuber Mark Rober guest-host the show, which led to the only possible outcome: a science-based prank involving elephant toothpaste.

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For the prank, Rober brought in “Science Bob” Pflugfelder and Guillermo to help fill Kimmel’s office at the show with the toothpaste, which is made from hydrogen peroxide and creates a wildly expanding foam.

To get things going, they called Kimmel up and had him watch Guillermo do the experiment in his office, which involved dumping liquid from one bucket into another and watching the green foam blow up to take up a huge part of the room.

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“It’s not gonna disappear now or something?” Kimmel laughed, after the experiment, adding, “My attorneys will be in touch.”

He also warned Guillermo that he’ll be seeing him when he’s back from vacation.