Love is like a video game.
Both sported mustaches, and Fallon wore the trademark red Mario hat. "You be my Princess, and I'll be your Toad, I'll follow behind you on Rainbow Road," Fallon crooned.
"You be my Toad, and I'll be your Peach and I'll follow behind you on Koopa Beach," Gomez sang back.
Ever the gentleman, Fallon sacrificed himself for his lady. "The blue shell is coming, so I'll go ahead, if you hang behind, it'll hit me instead," he sang.
Several times, Gomez almost cracked up. But she kept it together to harmonize the chorus with Fallon: "The finish line is just around the bend; I'll pause this game, so our love will never end."