Hey, David Letterman
: pick on someone your own age! The Late Show
host welcomed Justin Bieber
to his program last night and gave the 18-year a very hard time about his tattoos, considering Justin just got a fresh one that reads "Believe" across his left arm. "Don't go nuts," Letterman advised, regarding Bieber's influx of ink. "Because more and more you see like the mural ... like the Sistine Chapel, it's too much." It's okay, Justin ...