In 2022, the chef Jean-Georges Vongerichten was working in the kitchen of Happy Monkey, his restaurant in Greenwich, Conn., when an employee pulled him aside. A critic was coming in.

“I’m always nervous when someone tries my food,” Mr. Vongerichten said. But this time was different. The critic was 8 years old, and he planned to order an item that wasn’t on the menu: a Shirley Temple.

After perfecting arroz con pollo and sour cherry mole, Mr. Vongerichten admitted that America’s favorite mocktail had slipped through the cracks. “The Shirley Temple is not something I grew up with in France,” he said. “We were not prepared.”

Mr. Vongerichten and his team invented a Shirley Temple recipe at the eleventh hour using small-batch grenadine, homemade ginger syrup and Tajín seasoning. The critic awarded it a 9.3 rating.

This is the effect of Leo Kelly, now 11, who has been reviewing the drink for roughly half of his life as the “Shirley Temple King.” In short videos on Instagram, and occasionally on TV, he ranks Shirley Temples on a 10-point scale, considering factors like color, carbonation and the quality of the grenadine.

The internet is awash with food reviewers who opine from dining booths and drivers seats. But perhaps few of them have studied a single item the way Leo has.