Walt Disney Animation Studio is celebrating its 100th anniversary with a one-of-a-kind short, Once Upon A Studio bringing together characters from all across the studio's legacy. When the Walt Disney Animation Studios employees leave for the day, Mickey and Minnie escape to take their pictures on the wall. They set out on a quest to bring together 500 other animated characters for a group picture.

Dan Abraham and Trent Correy helmed this short as both the writers and directors. Once Upon A Studio is produced by Yvett Merino and Bradford Simonsen. The short features countless returning Disney animation legends, including Jodi Benson, Josh Gad, Jeremy Irons, Bret Iwan, Paige O'Hara, Anika Noni Rose, and Alan Tudyk.

Related: Mickey Mouse Was Walt Disney's Second Attempt At An Icon: This Character Was First

Producers Yvette Merino and Brad Simonsen spoke with Screen Rant about working on Once Upon A Studio. They shared the mind-blowing moments where they were able to work with their Disney heroes and incorporate lesser-known characters into the short. Merino also teased a heartwarming moment between Mickey Mouse and Walt Disney in Once Upon A Studio.

Yvette Merino & Brad Simonsen Talk Once Upon a Studio

Screen Rant: Once Upon a Studio isthe perfect way to honor the hundred-year anniversary of Disney and Disney animation. Are there any lesser-known characters that you were excited to include in Once Upon a Studio?

Yvette Merino: Yeah, I mean that was the exciting part of making this film is like, "Oh, we can get characters who don't always get the spotlight." I have a young daughter and so she knows very well who Ariel is, who Belle is and all of the big characters, but there are fans out there that love Treasure Planet. There are fans out there that love Chicken Little, and even my husband in particular, there is a short from a long ago with Pedro the Plane and he was like, "Oh, I hope Pedro, the plane is in there." So we were excited to get as many in as we could.

Brad, can you talk to me about the challenges of bringing these different animation styles together? Because the animation style stays true to the form in which we saw these characters, rather than making them all the same type of animation. So you guys really did a good job of blending these different animation styles. So can you talk about that a little bit?

Brad Simonsen: You bet. Yeah. So Dan and Trent knew going in that that was the number one priority. We wanted these characters to feel a hundred percent like they did in their very first movie. So, we really were very thoughtful about bringing people together that understood both the history and the process. So people like Eric Goldberg we brought in and said, "Okay, if we want to do a scratchy scratchy line or if we want to do a Xerox line or what type of income paint was used, how did we do this?" So that was the process really of discovering and then reinventing our pipeline for hand drawn.

And then as that evolved, we were like, "Okay, now they're interacting and now they're living in this world that we live in. How do we make sure that that works?" So we went to great pains to do test shots where we had CG characters and 2D characters of those different eras interacting and then really meeting using the production designer to say, "Hey, this is what we need to do. I think this is the type of highlight that we get." And we just really were careful and cared and listened to every note as we did it. Yeah.

There's a great elevator scene that I won't give away, but it made me wonder. How did you guys choose the different dynamics of using these different Disney characters that have never met before together, and how did you guys come up with those groupings?

Yvette Merino: Yeah. Really a lot of it is Dan and Trent had this vision from the very beginning, and without giving too much away, they really thought of, "Okay, who is going to be the most opposite to Donald Duck and who would really just get at him?" That was the start of it. Talking about the people in the elevator and how it was an opportunity, one to get those lesser scene characters in a featured shot, but also, who.

If you have Mother Gothel back there who is, if you watch, rolling her eyes and just annoyed at it all and all the different characters, and what I love is they all keep their true personality to who it is. Even with Baymax coming in at the end, it's just so innocent I'm like, oh, "I'm going too." And so it's one of my favorite scenes.

You have so many Disney legends returning for this, and unfortunately there are a handful that are no longer with us. Can you share your experience recording with some of these Disney legends? Then, for the ones that are no longer with us, how did you bring them into the fold? Because they sound just as I remember them.

Brad Simonsen: Yeah, I'll start with that part. Everyone we reached out to that was alive and able to do the work actually said yes, so that was super exciting. For the ones that were not available, we do have a group that we go to for sound alikes, so we do look and find someone who sounds like it and then we record them. It's really that simple of a process. Dan and Trent were incredibly particular and looked and really tried to find that voice that matched perfectly, once again, to fulfill that feeling of when you first meet those characters.

In regards to the recording of who were our heroes, Yvette and I both have our experiences as we were recording these where our hearts just kind of flew out of our chest. Mine actually was Winnie the Pooh. We got to show them the short and they got to react, so we got to have a moment with them where they saw it and relived this experience with us. That was incredibly profound and meaningful, and then we got to watch them perform and it's like watching your heroes. So it was amazing. I don't know, Yvette, if you want to share one of your stories about that too.

Yvette Merino: I mean, it was just a history of my growing up of like, "Oh my gosh, Jody Benson. I get to meet Jody Benson." Just so many. I worked on Big Hero Six and Baymax as one of my all-time favorite characters. So we were recording Scott Adsit to come in and do that voice again, was great. It was truly a dream project.

Yvette, can you talk about this version of Mickey we see, and how you guys settled upon this version of Mickey that's in Once Upon a Studio?

Yvette Merino: Yeah, I think it was a choice that Dan and Trent make, looking at all the different histories of Mickey, and this one felt like it was a good one. It's from Mickey's birthday party where they kind of jump out of the thing.

One of the things is they wanted to make him look like an everyday Mickey that we see, but also we have that special moment with Walt, and he takes his hat off and really just has that moment with Walt. That was a part of it too, because he doesn't typically have a hat on. There's obviously a lot of thought that went into it, but really this one would just kind of represent an everyday Mickey that we love.

There has to be a moment in the process of working on this where you just sit down and realize, "I'm working on this short film that is really a celebration of the last 100 years." When did you guys have that 'pinch me' moment that, "I'm working on this with all these classic Disney characters?" We'll start with you, Brad.

Brad Simonsen: Every day.

Yvette Merino: Yeah, this was insane.

Brad Simonsen: Literally every day. From the minute Yvette and I were told that we could be on the show. We both asked at the same time to be on the show. We were literally like, "Wow, this is really meaningful." But then every single day, you'd have these moments where you'd have some icon show up or some character. I'll give you an example of Bambi. When we saw the pencil test of Bambi come in, literally we're sitting in the room and we all giggled and like, "Oh, here. This is crazy." So yeah, it really hits you. Sorry, Yvette. I'm using all the time.

How about you, Yvette?

Yvette Merino: Yeah. No. I mean, honestly, that was really my immediate thought is every day. It was when Dan and Trent shared it and pitched it to the studio, both Brad and I reached out to Clark Spencer, our president, and said, "We did it separately without knowing. I have to work on this." What a gift to actually be here, to be a part of Disney animation during this moment, but to be a part of this film was really, truly special. I feel like we're standing on the history of what everyone else has built, and so we just wanted to honor that and the past Disney.

About Once Upon a Studio

When two new employees stay at the Walt Disney Animation Studios overnight, they will see all the Disney characters from the past and today come to life, and get all gather up for their very own picture taken for their 100th anniversary.

Check out our other Once Upon A Studio interview with directors Trent Correy & Dan Abraham.

Once Upon A Studio will debut on ABC on October 15 at 8/7c and be available to stream the next day on Disney+.