From Long Island to “The Little Couple,” Bill Klein has been living large. The online pet-supply entrepreneur and his wife, neonatologist Dr. Jennifer Arnold, each was born with spondyloepiphyseal dysplasia, a rare skeletal condition for which they’ve had more than 50 surgeries between them. Yet while Klein is just 4 feet tall and Arnold is 3-foot-2, they nonetheless have gone on to have successful careers, adopt two children, star in the long-running TLC reality show “The Little Couple” and write books.

A pinnacle of their achievements is their book-promotional appearance Tuesday in Rockville Centre, at the Madison Theatre at Molloy College — because what’s better than a local-boy-makes-good returning home? While his life may be an open book — two of them, actually, with his and Arnold’s 2015 memoir, “Life Is Short,” and now “Think Big: Overcoming Obstacles with Optimism” — he can still offer rare tidbits about growing up right here.

5 THINGS YOU DIDN’T KNOW ABOUT BILL KLEIN OF ‘THE LITTLE COUPLE’

1. He was raised in Port Jefferson Station. But he was born Oct. 13, 1974, in Bethpage.

“I arrived in Port Jefferson Station with my folks when I was about a year old,” he says.

2. His father was a police officer for a now-defunct department.

advertisement | advertise on newsday

“My dad was cop in the Laurel Hollow Police Department. Now it’s [contracted out to] Nassau County. My grandparents lived in Massapequa, right off Broadway.

3. Klein attended grade school at Boyle Road Elementary . . .

“My mom had a house that was very, very close to the school, so that I wouldn’t have to struggle with school buses if I didn’t want to, and so that I could walk home and it wouldn’t be a long distance.”

4. . . . where, for a part-time job while attending Comsewogue High School, he was a janitor.

“I pushed a broom for four years as a way of putting gas in my car. They had a program through BOCES [New York State’s Board of Cooperative Educational Services] or something like that, that facilitated kids with different types of disabilities getting work. And frankly, I think there was a little bit of taking advantage [by] the organization because the pay sucked when I first started. But I matriculated to a regular part-time position there and worked from 3 to 7 p.m. five days a week. I couldn’t get away from that darn school until I went to college! [laughs] Sixteen toilets a night — that was part of my gig. One third of the building was mine [to clean].”

@Newsday

5. Once during elementary school, when he was in a full-body cast for months after a surgery, his classmates made a field trip to his home.

“So you’re laying down horizontal for about three months [in] a hospital bed on the first floor of the house and a wheelchair that lays flat. My mom used to bring me outside to the backyard so I could get some fresh air during the day while school was in session. One of the teachers decided that they were going to do a field trip to my house for lunch and recess on one of those spring days. So rather than me being alone in the backyard, they brought lunch and cake over to my house and hung out with me for an hour or two in the early afternoon. Which I kind of think speaks to the kind of people who are on Long Island.”