It was a bright, seasonably cool Sunday afternoon, and as the light poured in through the windows of Sarah Jessica Parker’s newly opened shoe boutique at the South Street Seaport, so did the crowds. They were drawn to the candy-colored stilettos on display, and then found themselves in utter rapture upon seeing the star herself.

“I’m sorry, I’m not allowed to take pictures,” said Ms. Parker, her forehead crinkled in an expression of regret as a trio of late teens aimed their iPhones in her direction. “I’m so sorry.”

There were no pictures allowed because Ms. Parker was working — not on a set, but rather on the floor, crouched frog-like, fitting a pair of size 38 sparkly ankle boots onto a middle-aged woman visiting from Canada.

“They’re handmade in Italy, and the interior is nappa, which is really soft, so they’ll stretch,” she informed her customer, whose flushed cheeks matched the velvet poppy ottoman on which she was sitting. “Take a spin in them.”

Ms. Parker was wearing a different pair of disco-ball boots, hers a knee-high version called Studio that slouched around her skinny gray jeans. With her eyes encircled in shimmery green eye shadow she had applied herself that morning, she appeared luminous. Like a Disney princess, for adults.

“This is amazing! I love you!” squealed a willowy woman in spandex, dragging her slightly embarrassed, but no less delighted, husband behind her. “I just finished a 5K run. My feet are swollen, but I’m buying shoes!”

“That’s actually the best time to buy shoes — your feet are at their most honest,” Ms. Parker noted.

“Oh, and you’re good at sales, too!” the runner exclaimed.

Ms. Parker, who had no previous shopgirl experience, is what is known in the industry as a “shoe dog.” When her schedule permits, she hops on the subway and heads, unannounced, to one of her two New York stores — the other is a “temporarily permanent” space on 52nd Street — or a retail partner like Bloomingdale’s to peddle her wares for hours on end. Or until her kids come home from school.

“I don’t know how to be involved in another way,” Ms. Parker said. “I’m like that with my fragrances, with producing, with my children. To have one foot in the door, just checking in … That would feel fraudulent.”

Along with her business partner George Malkemus, who doubles as president and chief executive of Manolo Blahnik USA, Ms. Parker designs every uber-girlie pair herself, from the satin bow-tie mules to the rubber-soled T-strap sandals she calls a “sneaker,” posts every Instagram pic, and chooses every piece of flower-hued furniture for the stores. She even created the house soundtrack, which is filled with feel-good tunes like Whitney Houston’s version of “I’m Every Woman.” She hummed along while stuffing blush-colored tissue paper into a shopping bag.

The one aspect of the business she shies away from: closing the deal. “I’m not good at it, and I don’t want to be,” Ms. Parker said. “These are costly items,” she said (prices range from $250 to $600). “I don’t want anyone to feel like they were forced to buy them.”

No one had to nudge a woman from New Jersey to kick off her crystal-encrusted flip-flops and try on a pair of equally bedazzled ballet flats. “I’m so extra,” she said, adding that it was her birthday, as well as her 10-year anniversary of being cancer free. She was celebrating by having a “Sex and the City”-themed weekend, complete with dinner at Buddakan and a trip to Ms. Parker’s shop. Meeting “Carrie” was the cherry on top.

“It made my life!” she said.

Ms. Parker, head bowed, demurred. Later, after she had bade the birthday girl to wear the shoes in good health, she made it clear to a reporter that all the fuss and effusive praise was not so much for her, as for the lovable character she played on TV for six years.

“I’d be delusional to think it’s for me,” she said. “I got to be a part of something that was meaningful to a lot of people — and it’s that which allowed me to do this. Nobody would have otherwise said to me, ‘Do you want to be in the shoe business?’”

Her M.O., she said, is to meet the demands and dreams of those 10 million people who invited Carrie into their homes each week. Clearly she had done so for a young woman in head-to-toe black, who had just purchased a pair of red satin pumps, and grown faint from all the excitement.

“I need to go eat carbs!” she confessed.