When news broke that Once Upon a Time was finally doing a musical episode, it only made sense. After all, a number of the stars on the show are actually talented musicians. For example, Colin O'Donoghue will really be singing as Hook in OUAT, and Hook's song is going to be a big moment for the character. All of the OUAT cast members who are featured in the episode will be using their real voices, and for any of those who don't know, Colin O'Donoghue is an experienced singer and guitarist who's been performing for years. So there's no reason to expect a single off note in his song in the OUAT musical.
In 2003, O'Donoghue formed The Enemies, an five-member band, in his native Ireland. He sang and played guitar for the group, and they released their first album, The Enemies, in 2011. In 2013, O'Donoghue announced via Twitter that he was leaving The Enemies due to his filming schedule for Once Upon a Time, after 10 years of playing together. Since then, his time for original music has been limited, though you can occasionally find him playing a cover or two online, or find a clip of him breaking into impromptu song at a panel.
With those pipes, it's no surprise that the Once creators gave O'Donoghue a big moment to sing in the episode. The musical numbers appear because of the wish Snow and Charming made to save Emma, making everyone they interact with burst into song whenever they're expressing themselves. When they run into Hook at a local tavern, looking for someone who can lead them to the Evil Queen, Hook's song shows that in the past, he wasn't the type of pirate who was out for gold — he was motivated by "revenge" against the "croc" that tore off his hand, also known as Rumple.
And that revenge is going to be a big part of the other big event in the musical episode: Killian and Emma's wedding. O'Donoghue tells Entertainment Tonight that Hook's vows will reference his song. "I liked the fact that Hook doesn't shy away from the fact that he wasn't great at the start and he just wanted revenge. He just cuts to the chase and says Emma is the reason that he believed that he could love again," he explains. Of course, the Black Fairy is also looking for revenge, as in, looking to put another curse on Storybrooke... but I can't see this episode ending badly, even with all the other tragedy that has plagued Killian and Emma at every turn.
O'Donoghue will get the chance to sing (and dance) once more in "A Happy Beginning," a song that showrunner Edward Kitsis explains will show how important this wedding is for the whole town. "So for us, we wanted it start with [Emma and Hook singing,] but then stretch out to everybody because that is the core of the show," he tells ET. Unfortunately, you'll have to wait and see the full episode before you can see the whole performance of "A Happy Beginning," but O'Donoghue's singing is just one of the many reasons fans are so excited to finally get a musical adventure in Once Upon a Time.