Ylvis' performance echoed the motifs of the music video that made them famous. They wore fox costumes and frolicked around with a variety of animal creatures. Fallon even donned his own fox outfit for the end of their set.
Though Ylvis have been working as a musical-comedy duo since 2000, they were shocked by the success of their "Fox" single, now sitting at No. 6 on Billboard's Hot 100 chart.
"It was released to get some attention in Norway. Beyond that we hadn't even thought about it, it’s really crazy," they told Billboard last month.