Rob Lowe is royally disappointed in Prince William.
The ageless 55-year-old actor poked fun at the Duke of Cambridge's thinning hair recently after an interviewer from London's Daily Telegraph asked Lowe if he considered himself to be as vain as British men.
"That's a low bar,'' the "Class" star joked. "Can we talk about William? I mean the future king of your country let himself lose his own hair, so when I say British men set a very low bar ...
"Honestly, one of the great traumatic experiences of my life was watching Prince William lose his hair. He's going to be the f— king of England!"
The "Parks and Recreation" star still has a full mane, which he has maintained through any means necessary over the years.
"There's a pill!" he said. "The first glimmer that a single hair of mine was going to fall out, I was having stuff mainlined into my f— veins. And that's what I did for the next 30 years."
As for William, he has maintained a sense of humor about the subject amid grief from his wife, brother and royal watchers.
The duke recently made a joke of it himself following the birth of Prince George, 5, the oldest of his three children with Catherine, Duchess of Cambridge.
"He's got way more (hair) than me, thank God,'' he told reporters.
In 2016, William put a spotlight on his receding hairline when he opted for a close-cropped cut.
This isn't the first time an American celebrity has taken a shot at his balding pate. Pop star Justin Bieber bust his chops back in 2012, saying the duke should opt for some Propecia.
"You just take Propecia and your hair grows back," Bieber told U.K. magazine Rollercoaster. "Have you not got it over here?"