5:51am PT by Erin Carlson
Justin Bieber Bickers With David Letterman Over New 'Believe' Tattoo (Video)
Generations collided on Thursday's Late Show when Justin Bieber showed off his new tattoo, much to David Letterman's disapproval.
"How does that help how you look to have a tattoo?" the CBS late-night host asked the Canadian pop prince, 18, who had the name of his new album -- Believe -- stamped permanently in big black letters on his left arm.
"How does it not help the way I look?" Bieber responded, explaining that Believe's June 19 release was "an important day" so he wanted to mark the occasion.
In an awkward moment, Letterman suddenly grabbed Bieber's arm and apparently tried to rub off the tattoo. Objecting, Bieber yelled, "Eh! Eh!"
When Letterman backed off, the singer then looked out into the crowd, smiled and quipped, "Grandpas."
Bieber's latest disc, which has spawned the Justin Timberlake-esque single "Boyfriend," quickly jumped to No. 1 on iTunes. All week, he's been on a promotional media blitz from NBC's Today show to CBS' Late Show, where his dynamic with Letterman has become that of a kid forced to hang out with his slightly-out-of-touch grandfather.
"Do me a favor -- don't go nuts, you know what I mean?" Letterman said of full-body tattoos. "Because more and and more, you see the 'mural' and like the Sistine Chapel ... it's too much."
"I'm not going for the 16th chapel," Bieber added, to which Letterman joked: "Canadian high school!"
Watch the clip below.