A cashier just learned the hard way you never question a little girl's choice of doll.

Two-year-old Sophia has just reached a major milestone in her life: she’d been toilet trained for a whole month.

Her parents, Nick and Brandi, told her she could pick out a special ‘prize’ as a reward for all of her hard work.

But when she picked out a new doll, something…unexpected happened when her daughter reached the checkout of their local department store in South Carolina.

“The cashier asked Sophia if she was going to a birthday party,” Brandi wrote in a Facebook post about the experience.

"We both gave her a blank stare. She then pointed to the doll and asked Sophia if she picked her out for a friend. Sophia continued to stare blankly and I let the cashier know that she was a prize for Sophia being fully potty trained," she continued.

The woman, who Brandi said had a "puzzled look" on her face, then asked her daughter if she was sure that was the doll we wanted.

"She doesn't look like you. We have lots of other dolls that look more like you," the cashier said.

You see, the doll that blue-eyed, blonde-haired Sophia had picked had dark skin.

But Sophia, a symbol of all that is pure and good and right in the world, just didn't see the problem.

Before her mother could jump to her daughter's defence, Sophia offered the cashier a response.

"Yes, she does. She's a doctor like I'm a doctor. And I'm a pretty girl and she's a pretty girl," Sophia answered.

"See her pretty hair? And see her stethoscope?"

LISTEN: The restaurant that gives discounts to well-behaved kids.

The story made Brandi so proud, she had to share it on social media. Sophia's perfectly innocent response has now been shared more than 204,000 times.

"This experience just confirmed my belief that we aren't born with the idea that colour matters," Brandi wrote.

"Skin comes in different colours just like hair and eyes and every shade is beautiful."

Brandi wants everyone to know that she doesn't blame the cashier.

"I believe she was completely ignorant to what she was truly saying. I feel like in her mind she was being helpful and making conversation with my daughter," Brandi wrote in a follow up post on her Facebook page.

Out of the mouths of babes, right? We should all take a leaf out of Sophia's book.