It seems, particularly when everyone lives Happily Ever After, the typical response is to get everyone who was ever involved in The Hero's Journey, even if they only passed them on the street, together for a big celebration where everyone dances their feet off. Bonus points if the hero's enemies (and perhaps even the main antagonist, too!) attend the party. Mega points if it's in slow motion. The Hero, or a member of their True Companions, may sing the song we're all rocking out to. The writers might also decide to use this opportunity to clean up some romantic loose ends, or throw in some last-minute heel face turns.
If it starts before the plot is resolved, it's a Concert Climax. Compare Dancing Theme, which happens during the opening rather than the ending. Closely related to "Everyone Comes Back" Fantasy Party Ending. See also Sudden Musical Ending, "Everybody Laughs" Ending, Food End, Dancing Mook Credits. It can happen during a Wedding Finale if the wedding guests break into a dance. It may overlap with Big Finale Crowd Song if there also happens to big crowd song to go with the dancing.
Dance Party Ending has been suggested to play 2 roles. Click below to see other actors suggested for each role, and vote for who you think would play the role best.