When Stew Leonard opened what he dubbed a “dairy store” in Norwalk, Conn., in 1969, it was a wonder of marketing, with a petting zoo, animated Disney-style characters and an on-site bottling plant. There were serious retailing strategies as well—a limited product line, attractive house brands, slick promotions and an abundance of free samples. The concepts pioneered in that supermarket are seen today at Trader Joe’s, Costco and Whole Foods.

You’d think such an innovator would resent — even threaten legal action against — those who profited off his ideas. Not Leonard, who died last week at 93. He encouraged and even mentored food merchants around the world.

Having lived for a time near Norwalk, I came to know Leonard and his son, Stew Jr., who now runs the operation which has expanded to seven stores in the tri-state area. An eighth store, Tom Leonard’s in Glen Allen, Va., is operated by another son. The family once hired me to conduct promotional video interviews with customers. “I’m a journalist and I ask tough, critical questions,” I warned. Their response was, “We’re not worried.”

It turned out that the shoppers — some of whom had driven 100 miles for the experience — were uniformly positive. Indeed, they acted like kids at Disneyland.

Stew Leonard’s boldest retailing concept was to have a single aisle winding through the entire layout, taking shoppers past every item offered until they arrived back where they entered. No one runs in for a quart of milk or a single loaf of bread, which most supermarket operators count on, but the gimmick earned the store a place in the Guinness World Records for having the highest dollar sales per square foot of selling space.

People like Paul Newman, Martha Stewart, Frank Purdue and Sam Walton were among Leonard’s friends and admirers. That admiration was tested soon after his retirement in 1990, when customs agents in St. Martin found that his suitcase contained $70,000 in cash. It led to uncovering a tax-fraud scheme to divert $17.1 million by using a custom-made computer program that produced two sets of books. Cash was hidden in the fireplace in Leonard’s Norwalk office, then transported out of the country.

During his 44 months in a Pennsylvania prison, he persuaded officials to let him conduct retailing seminars—not just for inmates, but for merchants in nearby towns. He explained how in the 1920s his father, Charles Leonard, delivered milk by horse and buggy. Just 21 when Charles died, Stew took over Clover Farms Dairy in Connecticut and began honing the marketing skills that would make him rich. Delivery trucks were fitted with animated cow heads on top that made sounds. Painted on the sides of the trucks: “You Wave and I’ll Moo!” He bought out a neighboring dairy and doubled his business. But the popularity of home-delivered milk was fading, so he borrowed as much as he could to build what many would later refer to as “The Disneyland of Dairy Stores.”

His prison lecture also outlined his core business philosophy, STEW: S-satisfy the customer; T-Teamwork gets it done; E-Excellence makes it better; W-Wow makes it fun.

Stew Jr. once told me his dad was truly sorry. He appeared to be a generally decent man who got caught up in what he foolishly convinced himself was a victimless crime, served his time, and tried to pay back. Customers I spoke with were saddened, but quick to forgive.

And that had special meaning at Stew Leonard’s, where a three-ton chunk of granite in front of the store has the inscription: “Rule #1: The Customer is Always Right”; Rule #2: If the Customer is Ever Wrong, Re-Read Rule #1.”

Peter Funt’s latest book is “Playing POTUS: The Power of America’s Acting Presidents,” about comedians who impersonated presidents.