James Corden, the host of “The Late Late Show” and new host of the Grammys, made quite an entrance, falling down a flight of stairs on the stage after a comic bit revolving around technical difficulties involving a hydraulic lift.

The show had other moments of levity. When Tyler Joseph and Josh Dun of Twenty One Pilots won best pop duo/group performance, they immediately stripped out of their pants and walked to the stage in their underwear.

Mr. Joseph explained that before they were famous, the two had watched the Grammy awards in their skivvies and pledged that if they ever won, “we should receive it just like this.”

He added: “I want everyone who’s watching at home to know, you could be next. So watch out, because anyone from anywhere can do anything.”

After the commercial break, Mr. Corden appeared pantless too.

Later, in a tongue-in-cheek exploitation of his popular “Carpool Karaoke” skits, Mr. Corden stood in the aisle of the Staples Center with a makeshift car frame around him, and, in a moment reminiscent of the selfie at the 2014 Oscars, gathered celebrities around him. Jennifer Lopez, John Legend, Keith Urban, Tim McGraw, Faith Hill and Neil Diamond sang Mr. Diamond’s “Sweet Caroline,” with the entire arena shouting along.