The host of the Late Late Show packed into his SUV with the Biebz for a round of carpool karaoke that included an impromptu dance number to his song "Baby."

Corden's Ludacris impression is pretty spot on, too. But, it's the guys' grand finale of Boyz II Men's "End of the Road" that you need to stick around for. Just perfect harmonies from these two.

For a minute, though, Corden admits he wasn't sure if it was actually Bieber who was riding shotgun."When I picked you up I didn't recognize you for a minute," Corden says. "Because you had a top on."

This leads the two to chat about his Calvins, which Bieber says he does have quite the supply of (boxes and boxes)--a situation that comes in handy as it allows him to only wears his underwear once. Yes, Bieber throws out his underwear after every wear. "I definitely don't wear them twice," he says, though the smile he gives leaves us skeptical about how true that statement actually is.