It seems to be an unwritten rule that genre shows will eventually do musical episodes (I’m sure you can think of your own examples so I won’t make a list). Since Once Upon a Time is also a Disney show I’m surprised it took six seasons before the Storybrooke Avengers broke out in song.
SPOILERS FOR THIS WEEK’S EPISODE
I’m not big on musicals in general but the gimmick worked for this episode where some of the singing actually made sense in context. The Blue Fairy made everyone in the Enchanted Forest sing for a day while Snow was pregnant with Emma so the power of song would help Emma later in life at a crucial moment - which conveniently was also in this episode. At the end we also get the wedding of Emma Swan and Killian Jones (aka Hook) complete with obligatory musical number just before the Black Fairy’s curse is unleashed on Storybrooke. (Next week is the season finale and presumably the defeat of the Black Fairy. So even if Emma Swan isn’t back if the show gets another season at least she got her happy ending.)
The songs are easily forgettable but Lana Parrilla looks to be having a blast vamping it up as the singing Evil Queen. And she gets to use a word you usually don’t hear on a Disney show.