In Finding Dory, the long-awaited sequel to 2003’s beloved Finding Nemo, anxious clownfish Marlin and forgetful blue tang fish Dory once again embark on a quest across the ocean. This time, however, it’s not Nemo they’re looking for; it’s Dory’s family.

For director and writer Andrew Stanton, a member of Pixar’s coveted brain trust and the genius behind Finding Nemo and Wall-E, Finding Dory was a personal and professional challenge. Stanton and his team at Pixar spent over four years on Dory, in the hopes of creating something that could stand on its own two fins — and for a funny fish tale, they delivered something surprisingly human. Finding Dory isn’t just a sequel; it’s an emotionally complex, beautifully wrought continuation of Dory’s story. Does it fall into familiar Pixar tropes? Yes. But there’s a lot of depth in these waters.

MTV News chatted with Stanton ahead of the film’s home release, and the director opened up about the one scene that became the bane of his existence, the importance of adding surrogate Dorys to the story, and his reaction to the film’s surprising star: Baby Dory. Plus, MTV News has an exclusive (and hilarious) deleted scene from the film, in which Dory thinks she’s home.

When you were making the film, did you know that Baby Dory was going to be the breakout star?

Andrew Stanton: I didn’t until near the end. We had our first screening with a test audience in November of 2015, and when we showed it to the audience, they literally screamed like it was a One Direction concert when they saw her. At first, we were like, “What the heck?” But then we realized that she was so appealing that we don’t want to audience to know that she exists. What made that so wonderful was seeing the test audience so surprised and elated by her, and I just wanted everybody to have that pleasure. To their credit, Disney marketing was really kind, even though it was hard for them at first to not put Baby Dory in any of the advertising.

There’s a scientific explanation for that, isn’t there? People think babies are adorable, and Baby Dory’s physical features — large eyes, a small jaw, big head, and young voice — are a perfect recipe for cuteness.

Stanton: That’s our producer’s youngest daughter, and she just had the cutest little voice. She was 4 when she started recording and 6 and a half when she finished. Fortunately, her voice didn’t change. But her mom, Lindsey Collins, has always been the scratch voice for Dory, so it was the easiest time I’ve ever had directing a child star because she would just put on her headphones, her mom would read her the line, and she would just mimic her mother.

I know that when recording Toy Story, Tom Hanks recorded so much excess material as Woody that you guys actually used some of those sound bites in Toy Story 2 and Toy Story 3. Was it the same with Ellen DeGeneres and Dory?

Stanton: Yep. And [voice of Marlin] Albert [Brooks]. There’s a lot of stuff that we can pull from, especially weird, little things like vocalizations and ways they laugh. But sometimes there are little gems that we can’t use in the film, so we find a way to use them in another. There are maybe 40 hours of dialogue in each movie for each of those actors, so it just takes forever to find it. You don’t know what you’re sitting on.

So were there things that were recorded during the first film that you used in this film?

Stanton: The first line you hear is Dory saying in her sleep, “Klaus, the piñata is drooping.” That is from the first time we ever had Ellen make up stuff for when Dory is asleep in the diving mask when they were hanging from the sub after the mine had exploded [in the first film]. I had always wanted to use that, but we had an embarrassment of riches, so we had to pick our three favorites for Nemo. So I was happy to go back and use that take I had always liked for this one.

There’s always one sequence in every animated film that’s the bane of every animator’s existence. I heard that at Pixar you guys call this your “Yeti’s cave,” when you just can’t get something right. What was your Yeti’s cave for Finding Dory?

Stanton: It was called “Stroller Crossing,” the scene where they cross the park in the stroller. That was the bane of my existence. We rewrote that scene more than any other scene. It doesn’t surprise me; that scene is about midway through the movie. Any time you’re near the halfway point of a movie and you think you know where it’s going, the audience wants to know, “Well, how are you going to get there?” The film can risk being boring if you’re just trying to travel to connect the dots. That usually means you haven’t solved certain things with your story yet. Sure enough, that was “Stroller Crossing.” Matter of fact, if I say those two words to my writer I think it will give her hives.

How many variations did it go through?

Stanton: At least 10, if not 15. How many times did it make it up to the screen, storyboarding it? I know 10 for sure. It went through many more drafts. Each scene had multiple rewrites, but there’s always one that, no matter how many times you tackle it — it’s like that one, unruly kid in the family. It just keeps rebelling and climbing out the window.

There are so many characters in that sequence. Was that part of the trouble?

Stanton: That ended up being the solution. Those were three different scenes, and then we figured out a way to intertwine all of them so that it was one scene with all of them involved. That was one of the big breakthroughs on it.

Speaking of breakthroughs, did you realize at the time that animals driving trucks would be such a huge trend in 2016?

Stanton: [Laughs] No! I’m a little embarrassed that we didn't come across as that original, but I knew that inherently on its own it was going to be hilarious to watch an octopus try to drive a truck without being able to see the road and only having a fish with short-term memory as his guide. Who wouldn’t want to watch that no matter how many times you’ve seen an animal driving a truck?

Obviously, the film went through a lot of changes in four years. Was there one scene in particular you were sad to let go from the final film?

Stanton: There was a sequence. I always miss the stuff that’s very personal and small but packs a lot of emotion. There was a period of time, very early on in the first two years, where Destiny was originally going to be Dory’s half-sister. She was adopted by Dory’s short-term-memory parents because they only had this vague memory of missing something and they were going to come across this stray, wounded whale shark. I just loved the idea that Dory was insecure and intimidated by her replacement, who is literally the size of the reef. There was a moment when they had a sleepover, and they had pillow talk in the middle of the night like best friends do. The intimacy of having these two fish and the sway of the water ... I always miss the feeling of that moment.

The film received a bit of criticism over the treatment of two quirky characters in particular: Becky and Gerald. Some people thought that maybe the film was poking fun at them. How did you approach those characters in the writing process?

Stanton: We wanted to make sure that they didn’t come across like they were being treated poorly for being different. But there’s always an odd person out. What we were trying to do was make surrogate Dorys, make characters that you judged too soon and thought that they weren’t as capable as they really were. Becky is more capable than certainly Marlin had given her credit for. Gerald was more for humor, and all we cared about at the end of the day was that he got to win against these lazy sea lions. There’s some nice wish fulfillment to something like that. We did talk about that several times, to make sure that we weren’t crossing a line, but it’s very personal, so for some people, the line can get crossed in a different place. At the end of the day, all you can do is go with your own moral compass.

The film created a lot of surrogate Dorys. We see that in new characters like Destiny, Hank, and Bailey, too.

Stanton: The bigger thing is we wanted them all to underestimate themselves because that was the biggest thing to conquer for Dory, was her to believe in herself more, to find out that even she was more capable than she thought. That’s why I knew, no matter how much the story changed — and it changed a lot — that at her lowest point in the story she had to be all alone, with no more memory and no help and figure it out. That would be the only way that I, as a parent, would be able to sleep at night, knowing Dory will be OK in any situation that she’s in for the rest of her life.

Finding Dory is out on Digital HD on October 25, and DVD and Blu-ray on November 15.