PORT ST. LUCIE, Fla. — Here’s something the Mets have learned about Yoenis Cespedes: He has a few endearing quirks. For example, he likes waffles, but not square ones.

They’ve gotta be round.

It’s unclear exactly why. Perhaps he thinks they’re bad luck. But it’s enough of a sticking point that on Wednesday morning, Cespedes wondered if a Mets staffer might be willing to make a quick run to the store for a round waffle maker.

One of the reasons that Cespedes is so well-liked by the Mets is that despite his stardom, he comes off as a down-to-earth guy. Consider the waffle-maker search, when Cespedes insisted that the staffer take his black Lamborghini Aventador — the one customized to have flames shoot out of the tailpipe.

According to MLB.com, the car is worth $397,500 with an additional $80,000 in customization. It was the third ride Cespedes took to Mets camp in four days. He began the week with a Ford F-250 (worth about $60,000) before changing it up Tuesday with a three-wheeled Polaris Slingshot (customized price tag: roughly $61,000).

Then came the Lamborghini.

So, if you happened to be in Port St. Lucie, and you were one of the folks to snap iPhone pictures of that Lambo randomly parked in front of Walmart and Target (turns out Walmart was out of waffle makers), you can thank Cespedes and his preference for round waffles.

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The Mets have accepted Cespedes’ various quirks, and he repeatedly has cited his comfort level with the organization as one of the reasons that he returned.

There was a time when Cespedes’ flamboyance might have clashed with the sensibilities of Terry Collins, who was notorious for his various rules when he managed the Astros and Angels. In both places, his tenure ended with players grousing about his managerial style.

But with the Mets, Collins has relaxed those rules, and Cespedes has flourished in that environment. “You smother them,’’ Collins said, “they’ll want no part of that.”

Cespedes has been known to smoke cigarettes in the dugout before games. He rarely has taken batting practice on the field with the rest of his teammates. He golfs on game days. But the consensus has been to give Cespedes his space.

For Collins, after Cespedes’ seamless transition to the Mets clubhouse last season, there has been no reason to change.

“Every day he’s been here, he’s had a smile on his face,” Collins said. “Every morning he’s been here, it’s ‘Hey, skipper!’ He’s happy and that’s what you’ve got to have.”

Collins remains a stickler for the uniform, and he said he may approach Cespedes about wearing his cap properly on the field. (He’s known to wear it backwards or even dispense with it altogether, as he’s done this week, when he has worn a black skullcap.)

But even then, Collins wants to make the larger point clear.

“I just want him to be himself.”