Whether a sign of recession, regression or both, a few adults in Brooklyn have gotten into the lemonade-stand business this summer. Add it to the list of childhood pursuits that grown-ups now take seriously, along with cupcakes, T-shirts and Transformers.

NEW YORK — It’s an indelible image of summer: lemonade and cookies on a folding table on the sidewalk, a jar crammed with dollars, passers-by smiling politely.

A 40-year-old man selling lemonade.

Whether a sign of recession, regression or both, a few adults in Brooklyn have gotten into the lemonade-stand business this summer. Add it to the list of childhood pursuits that grown-ups now take seriously, along with cupcakes, T-shirts and Transformers.

Michael Orobona, a restaurant consultant who celebrated his 40th birthday this month, has been setting up a table outside his apartment in the Park Slope neighborhood every weekend this summer. He said he originally intended to strike a partnership with some neighborhood children in a mutually beneficial joint venture but refused to let their lack of interest dissuade him.

“I’m getting to know my neighbors and my community,” he said on a sweltering Saturday afternoon, selling what he said was organic lemonade to a woman in a floral dress ($4 for a 24-ounce cup). “I don’t just sell them lemonade, I tell them about my life.”

Orobona, a stocky, gregarious man with black-leather sandals, sells three kinds of lemonade, plus iced coffee, iced tea, Rice Krispies Treats and freshly baked chocolate-chip cookies (two for $1). There is a tip jar for customers looking to further reward his pluck.

A few blocks east, in the shadow of parked food trucks, sat Jim McMahon, a sophomore at the University of Rhode Island. His homemade sign read, “College Tuition Smoothies, $4.”

McMahon, a Park Slope native, has set up shop on the stoop of his family’s brownstone every weekend afternoon since early July with a blender, some fruit and a sunny disposition.

“I love smoothies; my parents love smoothies,” McMahon said. “Everyone loves smoothies.”

The blurring of childhood and maturity has long been a theme in Park Slope. It was here in 2008 that parents raged against a local bar that tried to ban strollers during happy hour. And good luck telling the difference among members of the X, Y and Z generations based solely on their taste in sneakers or skateboards.

Pop-up refreshment stands have some history here, as well. When the New York City Marathon runs along Fourth Avenue every year, residents on adjacent streets frequently set up tables with hot chocolate and bagels to profit from the gathering crowds.

But enough to quit your day job?

“I realized that if I sell three (smoothies) an hour, I’ll be making more than I was at Staples,” said McMahon, referring to the summer job he quit last week.

He is focusing on the smoothie trade full time.

Orobona is branching out, too. His first “franchisee” — a 16-year-old boy who prefers to remain anonymous — opened for business in Carroll Gardens this month. And Orobona plans to install a table on a nearby corner soon.

“If I tell you how much I make, people won’t want to buy from me anymore,” Orobona said.

.”