Playing Luigi is a secretive job.

On Wednesday night, Charlie Day appeared on “Jimmy Kimmel Live!” and was asked about his role as the green-hatted brother of video game icon Mario in the upcoming animated movie.

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“I’m playing Luigi. In fact, I just was recording that this morning, and I’d love to tell you all about it,” he said, “but they are top secret with this stuff.”

“Is that true?” Kimmel asked.

“Absolutely,” Day told him. “This is serious stuff! You know, these are Nintendo cartoons!”

Asked if he has read the entire script, Day revealed, “I know nothing. I know nothing. I show up and they’re like, ‘You say this and you say that,’ and it’s all very funny and good, and then I walk out and there’s two guys in overalls with hammers that are like, ‘You don’t tell nobody nothin’ about this, Charlie. I swear to God we’re gonna get your kneecaps, we’re gonna break your neck.'”

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Pressed on how the actor playing Luigi, such a central character in the franchise, could be kept in the dark about the movie’s plot, Day joked, “You know, Mario’s probably in the know. They don’t tell Luigi anything.”

Mario is set to be voiced in the film by Chris Pratt but Day explained that they don’t actually record together.

“They split you up!” Kimmel remarked, to which the actor said, “Maybe they just don’t trust me around Pratt, I don’t know.”