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Within the first few minutes of Tim Cook's appearance on "The Late Show," host Stephen Colbert was already threatening Apple's CEO.

The two on Tuesday were discussing Apple's new iPhone 6S, which launches next week, when Colbert asked whether Apple had again changed the charger on the smartphone. Cook assured him the company had not.

"Good, because I will stab you in the neck with a fondue fork!" the late-night comic blurted out.

Colbert managed to throw in a few more jokes during the interview. When Cook described 3D Touch, which makes the iPhone 6S touchscreen sensitive to levels of pressure, Colbert asked: "If I hang up hard enough on someone, will it actually hit them on the other side?"

"We haven't gotten there just yet," Cook replied.

Later, when Colbert asked Siri, the iPhone's digital voice assistant, "What should I ask Tim Cook?" Siri offered: "Do me a favor, ask him when I'm going to get a raise."

The show served as a venue for Cook to pitch the iPhone, by far the Cupertino, California-based company's biggest moneymaker. Getting attention for the September 25 launch of the latest models and keeping up sales of the device are critical for Apple's success, so expect Cook and other Apple executives to be on the campaign trail for a while longer. Ahead of the "Late Show" appearance in New York, Cook made an unannounced stop at the Apple Store on Fifth Avenue along with Apple Senior Vice President Eddy Cue. (Editors' note: "The Late Show" runs on CBS, the parent company of CNET.)

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Aside from the jokes, Cook spoke about former CEO Steve Jobs, who he described as having an "uncanny ability to see around the corner."

Cook also noted that he decided to come out as gay last year to show support for others and to try to prevent bullying and discrimination.

Colbert prodded Cook about rumors that Apple plans to build a self-driving car, something that Uber CEO Travis Kalanick referenced during his visit to the show last week.

"So, he's already given it away," Colbert said. "You guys aren't big on secrets. Tell me about it. Come on. Cat's out of the bag."

Cook punted on that one.

After just one week of shows, Cook was Colbert's third major tech CEO interview, following Kalanick and Tesla's Elon Musk.

During a Q&A with the audience before the show, Colbert was asked what other tech guest he would like to interview.

He jokingly answered Thomas Edison. Facebook CEO Mark Zuckerberg was suggested.

"Zuckerberg would be great," Colbert said, though adding that he could bring on Jesse Eisenberg, who played Zuckerberg in "The Social Network" movie "and no one would know the difference."