Jay Leno learned this life lesson from a pair of mystery underwear he found working at McDonald's

Tonight Show host Jay Leno during 'Headlines' segment on June 8, 1992 .
NBC | Getty Image

Jay Leno spent more than two decades in the spotlight as the host of NBC's "The Tonight Show." Today that career has afforded him luxuries like a collection of over 100 cars — including a McLaren F1 worth millions. And, he's the host of CNBC's "Jay Leno's Garage," where he tests out rare vehicles with celebrities.

But before finding fame and fortune, Leno started his career with a minimum wage job at a McDonald's in Andover, Massachusetts as a teenager.

The experience wasn't just a way to earn pocket money. While slicing potatoes for French fries and ringing up customers at McDonald's, Leno learned a lesson about business he says is still important today.

"I worked at a restaurant on Main Street for two years, from 1966 to 1968," Leno tells author Cody Teets in "Golden Opportunity: Remarkable Careers That Began at McDonald's." "This was back in the good old days when they still had roast beef and strawberry shortcake, which I was a huge fan of."

Each day, Leno would get to work preparing the chain's famous fries.

"The French fries had to be made from scratch. We had to cut what seemed like a ton of potatoes every day," he explains. "I had these massive forearms from cutting those potatoes."

One morning, while getting ready to start on this process, Leno walked back to the restaurant's storage room to grab a new batch of potatoes.

"Tom Curtin, the owner/operator, was with me," Leno says.

The two men noticed something unusual: "There, on top of the sack of potatoes, was a pair of underpants," he remembers.

"Sometimes crew members changed into their uniforms at work and somebody had apparently forgotten their underpants," Leno continues. "I expected Tom to tell me to throw out the top layer of potatoes and wash the rest. Instead, he said simply, 'Get rid of all those potatoes.'

"Get rid of that whole batch. Just get rid of all of it."

From the experience, Leno learned a lesson about success: You can never go too far to ensure you're producing a great product.

"That was very impressive to me," Leno remembers. "The standards for quality were quite high. It was one of those life lessons I never forgot."

In his career as a comedian, Leno himself held high standards for jokes and material.

After wrapping nightly episodes of "The Tonight Show," Leno would head home at 7:00 p.m. and continue writing jokes (taking breaks to tinker in his garage with cars) until late at night, according to a 1993 profile by CBS's "60 Minutes." Leno and his staff would comb through hundreds of jokes, whittling the set down to the best 20. Then, Leno would read the jokes in order into a tape recorder, re-listen to them all, and pick the exact wording and timing of every joke.

"I meet with the writers at about midnight or so and work until about 4:00 a.m.," Leno told "60 Minutes." "I sleep four hours, maybe five."

And on weekends, Leno was still practicing, doing stand-up comedy gigs on the road.

Leno said his work ethic was about getting the job done right: "If you have time to complain, you don't have enough work to do."

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CNBC's "Jay Leno's Garage" airs Thursdays at 10 p.m. ET.

Jay Leno has no debt thanks in large part to abiding by this one rule
Jay Leno has no debt thanks in large part to abiding by this one rule

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