In Devil May Cry 5, each character has a special taunt called 'EX Provocation' which has a particularly long animation in exchange for being worth a lot of points if you somehow manage to do the entire thing. Vergil's EX Provocation has him summon his Doppelganger, who begins dancing, much to Vergil's chagrin. If you use this against the final boss, they will stop attacking and dance with the Doppelganger, allowing you to perform the whole taunt for free. Considering that, actual spoilers, said final boss is Dante, it makes sense that he would indulge Vergil's repressed silly side.