While Diesel was doing publicity for "Guardians of the Galaxy," British radio station Capital FM presented him with Smith's "Stay With Me" lyrics and a backing track for the tune and set him loose. The "Fast & Furious" star gamely gave it a whirl, aiming for the high notes and everything.
"I don't know how I did that," Diesel said as his impromptu performance ended to a round of applause from the folks in the room.
At any rate, Smith really was a fan of the action star's efforts.
"First of all I thought it was going to be good, but when I heard it, it's the most hilarious thing I've heard in my life," the pop singer told the same radio station Thursday morning. "It's amazing. Brilliant. The falsetto!"
Smith said he and Diesel should do a duet one day.
"It would be amazing."
You can watch Diesel's full performance here.