WATCH: Shawn Mendes says he'd pay $500 For Justin Bieber's boxers

Of course, he belted out a few tunes too.

As Shawn Mendes begins his weeklong Late Late Show (US) takeover, he first had to complete the right of passage that is James Corden’s famous Carpool Karaoke.

The teen idol jumped into the passenger seat to chat to the TV host about Ice Hockey, Harry Potter, moving out and in a strange turn of events, Justin Bieber's’ boxers.