The performance on Wednesday night came as America's Ylvis-mania reached new heights, with the comedy hit jumping to sixth place on the Billboard charts, and becoming the country's most streamed song.
"Out next guests have the biggest viral video in the world right now," Fallon told the audience as he brought Bård and Vegård Ylvisåker on stage. "We are thrilled to have them here tonight to perform it live for the first time on late night TV."
The two brothers gave a considerably slicker performance than last month's impromptu rendition of the song on the Ellen DeGeneres show, bringing the original costumes from their YouTube video and using smoke machines and lasers to add to the atmosphere.
The show's presenter donned a fox costume during the performance, and danced along on the sidelines.
"Ylvis was amazing! Jimmy Fallon was completely lost during the program," Laura Johnson (32) told VG. "During the rehearsal before the program, he said that earlier this week he had had Paul McCartney as a guest, but that he was more excited about having Ylvis."
Story continues below…
The brothers appeared in the talk show alongside Alan Rickman, the British actor who plays the sarcastic potions teacher Severus Snape in the Harry Potter films.
The song has now had more than 103m views on YouTube. The last time a Norwegian song climbed so high on the Billboard charts was A-ha's Take on Me in 1986, which went on to reach number one.