For the past five seasons, Once Upon a Time has featured some seriously spellbinding costumes, and it's all thanks to the series' head designer: Eduardo Castro!

Castro, who is currently nominated for a Costume Designers Guild Award in the "Outstanding Fantasy Television Series" category, has been with the ABC drama since the very beginning.

"I never, ever thought that I would have been here for five years," the designer recently spilled. "It's been a wonderful journey and it's interesting to see how the show has morphed and grown."

To help get fans even more pumped for the highly anticipated 100th episode, Castro took time out of his fairy tale-filled schedule to give ETonline the exclusive secrets behind four of Emma Swan's (Jennifer Morrison) most iconic looks.



MORE: 'Once' Bosses Spill on Underworld Adventures and True Love's Kiss!



1. Lady in (Many Shades of) Red:



ABC

Emma Swan's red jacket has become an iconic piece of clothing on the hit drama, but the story behind the selection is what's truly surprising. "The original jacket was bought around the corner from my hotel room the day before we shot [the pilot] and it was a very inexpensive jacket," Castro shared. "It was like 89 dollars, and the jacket that we have grown into, that we've remade and redone, costs almost four thousand dollars!"

So, what makes this new design even more magical than the original? "It's a custom jacket that suits her body and it's my take on improving that jacket," Castro explained. "[Jennifer] wasn't in love with the first jacket, really. As we went along, we made improvements for her, and the jacket is a little sleeker and a little more sophisticated and it fits better and it's better leather."

Now, 100 episodes later, Castro has about "25 to 30" different versions of Emma's red jacket. "There are some that are a brighter red, a medium red, red brown -- there's quite a few," he said.

Looking ahead this season, fans can expect a special blast into the past starring Emma's signature look. "We just had a particular sequence where Emma has discovered her red jacket," Castro shared. "It's a flashback but the interesting thing is that the red jacket has morphed into a much more sophisticated design than the original jacket."



EXCLUSIVE: 'Once' Casts Another Pirate From Hook's Past: Captain Silver!

2. Storybrooke Chic Is Harder Than You Think:



ABC

In an interesting twist, it turns out that Emma's most casual looks in Storybrooke are actually the most difficult for the designer to create. "Everyday modern clothes are actually very hard to do," Castro confessed.

"It's actually quite nice and easy when we do the fantasy clothes," he revealed. "But really finding a T-shirt or a pair of jeans or a little dress or shoes is hard for everyday Emma. Thank God that there aren't a lot [of those looks] and it's not just Emma's everyday wardrobe, it's any modern pieces.

Castro added, "Emma hasn't had as much of an opportunity to wear the fantasy clothes. She did this year for the first time."

"The other day, Jennifer Morrison came up and hugged me and said, 'Oh my God, where were all those fairy tale days when I wore all those [modern] clothes?'" Castro recalled. "It is a lot easier to do fairy tale clothes because the actresses get all excited about putting corsets on and sparkly fabrics and there's an excitement about something that's not just off the rack."



WATCH: Hook and Emma Can't Stop Kissing in This Sneak Peek Clip!



3. Creating Camelot Couture:



ABC

When we asked Castro about another potential trip down the aisle, the head costume designer revealed another surprising secret: he hates creating wedding dresses! "I just never related to them, but we do more wedding dresses than anything," he explained.

"Well, we didn’t do a wedding dress this season, but we sort of did one on Jennifer Morrison," Castro recalled. "It was a white lace dress in Camelot."

Fashion Fun Fact: It was actually Morrison's idea to create the ethereal-inspired gown for Emma. "She had some ideas and she brought in some sheets and fabric ideas," he said. "Jennifer is very good at sending me ideas and we sort of work together and we morph a look together."

"It was a really a simple situation," Castro said of the dress' romantic design. "But sometimes, the simple situations are harder to do, so that took some time because it was all about the fit. I personally liked the ivory cape she wore in the show."



MORE: Colin O'Donoghue Talks Hook's 'Kindred' Love With Emma!



4. Deconstructing the Dark Swan Details:



ABC

Fans were floored when Once debuted Emma's Dark Swan transformation and it became a major part of the character's wardrobe in the first half of season five. But now that Emma is officially no longer filled with dark magic, Castro is thrilled to have a bit of a break from the costume.

"I'm fine with it being gone for a while," he said with a laugh. "I think it was a very treacherous piece to do and we re-did it a few times."

Oncers can look forward to a revamped version of the Dark Swan suit in upcoming episodes. "In the first part of the underworld, you'll see is the original idea, but then Jennifer really thought that it lacked texture," Castro said. "So we re-cut everything and did it out of more snakeskin and crocodile."

"It was a combination of things," Castro continued. "We took elements from this jacket and that jacket and morphed them together, so it's the same but re-cut to give it a little more texture."



WATCH: 'Once' Cast Laughs About 'Warped' Romantic Relationships



The 18th Annual Costume Designers Guild Awards will take place on Tuesday, Feb. 23 at the Beverly Hilton Hotel.

Once Upon a Time returns with its 100th episode on Sunday, March 6 at 8 p.m. ET/PT on ABC.

What's your favorite Emma Swan look? What is your favorite thing about the fashion on Once Upon a Time? Share your thoughts with @LeanneAguilera on Twitter.

Need more Once Upon a Time in your life? Press play on the video below to watch the magical cast laugh about the "warped" relationships on the show!

