A T-shirt showing the likenesses of former Mets first baseman...

A T-shirt showing the likenesses of former Mets first baseman and current team broadcaster Keith Hernandez and his cat, Hadji, taken in the SNY booth at Citi Field on May 5, 2018. Credit: Neil Best

Keith Hernandez has been famous for more than four decades, so he knows how to handle it. But what about his friend Hadji? Might his sudden rise to stardom go to his head?

“He’s always been a prima donna,” Hernandez said, dismissing any concern. “Hadji’s famous in the house. He’s like King Farouk.”

Hadji, 15, is a Bengal cat owned by Hernandez, 64, a partnership that has become a sensation on Twitter and beyond.

Last month a Mets fan showed up at a game carrying an oversized picture of Hadji’s face, and other fans posed with it for selfies. Oh, and the game was being played in Atlanta!

This all started on April 2, when Hernandez ended a 2 ½-year break from Twitter — with the exception of a tribute to his late friend Rusty Staub three days earlier.

The original idea was to promote his book, “I’m Keith Hernandez,” on sale May 15, and a Hernandez and Hadji-themed line of clothing and other items at KeithHernandezShop.com.

At that point Hernandez was such a novice that when a reporter asked whether it really was him that was posting, he was not familiar with verified accounts. His first handle was @kher8286, in recognition of his two World Series rings, but it later became @keithhernandez.

Hernandez soon veered off message and began weighing in on Mets matters, updating fans on his travels and, inevitably, posting pictures and video of his cat.

“They all want to know about Hadji,” he said.

Within a few days, Hernandez had 25,000 followers. As of Monday, he was north of 66,000, and his feed had been featured in Sports Illustrated.

“I always got A’s in creative writing and in English literature when I had to write essays,” he said. “I love to read, and I’ve always loved to write.

“The best class I ever took in high school was typing. For some reason, because I can type, it doesn’t interfere with my thoughts. It goes from here [in my head] right down to [my hands].”

Hernandez said now that he has succeeded in getting the word out about his online shop, he is being careful not to overdo promoting it on Twitter.

“I’m just enjoying it,” he said. “I’m having a lot of fun with it. I don’t read every response back. It’s hard when I’m working here [at Citi Field] and at home . . . I like to write and I try to be positive and optimistic.”

For a long time, Hernandez had no interest in social media beyond the Facebook and Instagram accounts he maintained because his three daughters used those platforms. “I’m not of that generation,” he said.

So what was the motivation to launch the shop that in turn inspired the Twitter feed?

“My motivation was I want to pay off my house in Southampton,” he said. “That’s my motivation. So when I retire I don’t have a mortgage. How about that?”

Hernandez prefers written tweets to videos, but one of his greatest Hadji hits was a video of them leaving the house to pick up newspapers, at which time Hernandez was not entirely put together.

“I don’t give a [expletive] about that, obviously,” he said of his unkempt early morning appearance.

Making a 15-year-old cat a star would appear to carry with it some risks. After all, cats have actuarial tables, too.

“He’s 15 and he’s very healthy,” Hernandez said. “He’s like a 4-year-old. He runs around like crazy.”

A recent visit to the veterinarian revealed a potential renal problem in his blood work. Medication was prescribed.

“The doc said he could live to 25,” Hernandez said of Hadji. “He’s in great health. I want to keep him around as long as possible.”