Fifteen years after Wicked took Broadway by storm, it's original stars Kristin Chenoweth and Idina Menzel have reunited to celebrate in NBC's A Very Wicked Halloween — and they're telling PEOPLE all about it!

Fifteen years after Wicked took Broadway by storm, its original stars Kristin Chenoweth and Idina Menzel have reunited to celebrate the Stephen Schwartz-penned musical’s legacy in NBC’s A Very Wicked Halloweenand they’re telling PEOPLE all about it.

The two actresses and Tony winners will host and perform on the show, which was taped on Oct. 16 at New York City’s Marquis Theater. They’ll be joined in the NBC special by a cavalcade of special guests — including Ariana Grande, Adam Lambert, Ledisi, Pentatonix and members of the past and present company of Wicked — to help celebrate the music and the magic of the show.

Chenoweth, 50, and Menzel, 47, were last back together in 2016, when they performed a duet from the show for the first time since they hung up their broom and wand after the 2004 Tony Awards.

Wicked opened on Broadway on Oct. 30, 2003, and has gone on to become a cultural phenomenon — winning over 100 international awards (including three Tonys) and earning over $4.6 billion in global sales, with performances in over 100 cities across 16 countries around the world. Over 55 million people have seen the show worldwide.

Based on the novel by Gregory Maguire, the musical tells the story of the witches popularized in The Wizard of Oz, but from their perspective. Book writer Winnie Holzman adapted the tale, while Schwartz penned its Grammy-winning score. Songs like “Defying Gravity,” “Popular” and “For Good” have gone on to be come mainstays in the musical theatre lexicon.

A Very Wicked Halloween: Celebrating 15 Years on Broadway - Season 2018
Kristin Chenoweth and Idina Menzel in A Very Wicked Halloween: Celebrating 15 Years on Broadway
| Credit: Virginia Sherwood/NBC
Opening Night of "Wicked" on Broadway
Kristin Chenoweth and Idina Menzel in Wicked in 2003
| Credit: Bruce Glikas/FilmMagic

Before hosting and performing on the special concert event, Chenoweth and Menzel sat down with PEOPLE and looked back on their time together in Oz.

PEOPLE: What has it felt like to return to Wicked?
Chenoweth: I never thought I’d be in anything that lasted 15 years, let alone 15 seconds. Nothing lasts this long. This has lasted longer than any of my romantic relationships! It’s amazing.
Menzel: It feels profound. It’s an honor to have this opportunity to commemorate Wicked, but it also forces you to look back on your life and see what the experience has taught you, where you’ve come from, what your journey’s been like … I feel very emotional and reflective.

You both set the standard for these characters that countless actresses around the world have worked to meet since. Was it as perfect of a fit right from the start?
Chenoweth: Right from the start! Very few times in our career do we have a hand-in-glove moment, and Glinda was mine. I just thought when I read it, ‘This is my part! And if anybody else plays Glinda, I’ll kill them in their sleep! [laughs]
Menzel: I remember I had to learn ‘Defying Gravity’ for my callback, and I started learning at home and I was crying to my ex husband who was working on it with me at the time. I really wanted it so badly. I would get chills when the music would start and the intro! I had no idea what it would become but I knew it was something special. I needed this role to teach me something about life that I needed to learn.

A Very Wicked Halloween: Celebrating 15 Years on Broadway - Season 2018
Idina Menzel
| Credit: Eric Liebowitz/NBC

What did you love about watching the other in the role?
Chenoweth: I loved watching Idina find Elphaba. We weren’t given the rules, we just had to find it. And that process — the things that didn’t work, the things that worked — that was a joy to be up close to witness.
Menzel: The good thing about working 8 times a week together is you get to see someone who is incredibly talented do their thing and learn from it. I learned from a comedic genius. Second to second, moment to moment, she’s just spontaneous and has such a feel — an arithmetic feel — for comedy.

Do you miss the green, Idina?
Menzel: Yeah… not so much. It was sometimes a pain in the ass, but sometimes it was great to get into character. I actually feel really beautiful in the green. The green, the way that they created the makeup look for it was very goddessy. I felt pretty Vogue in it.

What about you, Kristin: Do you miss the bubble?
Chenoweth: I was shocked when I woke up after I left that I still didn’t come and go by bubble. Where’s the bubble machine? What happened. I loved it. I had three minutes alone on the way up. It was slow moving and I was able to take those three minutes and really do my pre-show ritual — to get mentally prepared for what was to come.

A Very Wicked Halloween: Celebrating 15 Years on Broadway - Season 2018
Kristin Chenoweth
| Credit: Virginia Sherwood/NBC

Tell me about your favorite memory from working on the show.
Menzel: I would say probably opening night with Kristin. We had been workshopping the show for many years, and you never know with a show if it’s going to come to fruition. You go through all of these incarnations — and most of the time, shows go nowhere. So to finally be standing up there with her hand-in-hand, taking a bow, and feeling the love for the audience? That was really wonderful.
Chenoweth: That was our Madonna moment, opening night in San Francisco. Imagine Madonna, 1986, at Madison Square Garden. In my mind, that’s what it was. We knew then this was going to be something special. But it wasn’t until all the little girls showed up at the stage door, dressed in pink and green, that I realized this was bigger than just our little show. This was telling them something about life they needed to hear. And it’s had that affect on audiences for all these years.

Did you take anything with you when you left?
Menzel: Ooh I think I stole a couple things. I have my black hat, I have a broom, I have a green baby … I have a lot!
Chenoweth: I cannot confirm or deny what I have in my apartment to this day. [Laughs] I may have a wand but I cannot confirm or deny …

A Very Wicked Halloween: Celebrating 15 Years on Broadway - Season 2018
Kristin Chenoweth and Idina Menzel
| Credit: Eric Liebowitz/NBC

RELATED VIDEO: Go Inside Broadway’s Wicked for 15th Anniversary Production

You both sing songs from Wicked still in your solo concerts. Are the fans just as excited as they were on opening night?
Menzel: And then some. You know, it’s amazing because growing up, theater and pop were very separate. And ever since Rent for me, things have started to move in the direction where everyone just wants to hear good music, it doesn’t matter what it is. For us, even if our song isn’t played on the radio, if we can hold a microphone out and the audience can sing an entire verse back to use, we feel like rockstars.
Chenoweth: When I sing ‘Popular,’ there’s just that first note from the piano and they clap. I don’t even have to sing! I get applause. So I love it.

What advice would you give yourself back then, now?
Menzel: Stop apologizing and believe in yourself — believe that you are a good actress. I struggled with that doubt andI wish that I would have really learned to own who I was earlier.
Chenoweth: I had fun, for sure. I had a good time. But I wish I would have just enjoyed it a little more. Don’t think about what’s next — just stop and have fun.

A Very Wicked Halloween: Celebrating 15 Years on Broadway airs Oct. 29 (10 p.m. ET) on NBC.