Once Upon a Time's co-executive producers Adam Horowitz and Edward Kitsis confess to ET that bringing the musical episode to life from script to screen was a "really emotional" process for all involved.
"For us, we've been with them on this journey for 130-something episodes, so these moments where you're doing something new, it's exciting! It's really why you do it," Kitsis explains. "Every episode, you want to be you favorite episode and there was something magical about seeing these characters come to life and sing. And watching these actors getting to show off their talents that they normally don’t get to do, that was very inspiring for me and Adam and the rest of the writers and crew."
To help get you even more excited for Sunday's episode, entitled "A Song in Your Heart," the Once showrunners are sharing exclusive scoop on our five most highly anticipated songs!
1. "A Happy Beginning": "The inspiration was that we wanted this wedding to not just be about the two of them -- it's about this whole town," Kitsis shares of Emma and Killian's special moment. "How everyone is facing this together and how this family has come together. 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."
2. "Wicked Always Wins": "It's a solo for Zelena," Horowitz reveals. "She is amazing and Rebecca [Mader] does a phenomenal job with that song. We don’t want to give away exactly what is going in it, but it's all sort of pertaining to the stuff that is happening."
"I would say that this is Zelena's moment to shine," Kitsis adds. "And she's never been shy of the spotlight."
3."Powerful Magic": "I think that what I love most about [Snow and Charming's] duet is there is a very pilot feel to it in a sense," Horowitz says. "[Ginnifer Goodwin and Josh Dallas] were so excited to do the musical that when you watch them do their duet -- in fact, throughout the whole episode -- their enthusiasm is like you can feel it. You see it on their face, and they're so excited, and it really just makes them come alive. I don’t know how to describe it other than It's the Snow and Charming you love the most."
4. "The Queen Sings": "This is going to be an Evil Queen song," Kitsis confirms. "I think one of the goals for this episode was if you watch Once Upon a Time, you know that a Rumpelstiltskin episode is much different in tone than a Snow and Charming episode, and we wanted the songs to reflect the people who are singing them."
Kitsis continues, "So, 'Wicked Always Wins' is a Zelena song and the Evil Queen song is very much a Regina song. For the tone, I think we say it's kind of David Bowie meets Rocky Horror."
5. "Emma’s Theme": "Emma has a big solo," Horowitz dishes before adding that Jennifer Morrison sounds "amazing" on the track. "It is a super emotional song that really -- we hope -- kind of expresses essence of the character and, in may ways, sums up her journey thus far."
Once Upon a Time's musical episode airs this Sunday, May 7 at 8 p.m ET/PT on ABC.
Hey, Oncers! This article only contains a teeny, tiny bit of all the interviews that ET gathered while on set of Once Upon a Time's musical wedding extravaganza! So make sure you keep it locked to ETonline and follow @LeanneAguilera on Twitter for even more magical scoop this week!