Tonight Show host David Letterman has ridiculed pop star Justin Bieber's tattoos and lack of historical knowledge, upsetting the teen's rabid fan base.
Appearing on Letterman's long-running talk show on Thursday, 18-year-old Bieber revealed a new tattoo on his left arm, which bore the title of his newly released third album Believe.
Letterman was clearly unimpressed.
"Tell me that’s the last one," the 65-year-old said, prompting Bieber to reply, "It might be".
Soon after Letterman grabbed the teen's arm and pretended to rub the tattoo off.
But the interview's nadir came when Letterman warned Bieber, a Canadian, not to get more tattoos, as his body would come to resemble the painted ceiling of the Sistine Chapel.
"I'm not going for the sixteenth chapel look," the confused pop star replied.
A bemused Letterman seized on the gaffe with a joke about the Canadian high school system.
Bieber's fans, known as Beliebers, reacted with predictable outrage on Twitter, with many threatening to boycott Letterman's show.
Typical of the response was this tweet: "David Letterman was so rude to Justin Bieber very aggressive and stupid that old man should not be on TV anymore (sic)."