Kaia Gerber, ever-present model of the moment, has already had a busy start to fashion month, walking the runway for the likes of Tom Ford, Calvin Klein, and Proenza Schouler, among many others. But on Wednesday morning, the final day of New York Fashion Week, the 17-year-old was taking a runway break to promote another very special fashion line: her Kaia Gerber x Karl Lagerfeld collection, which the model was bringing to New York with an in-store signing after officially launching in Los Angeles earlier this month.

"I'm from California, so that one I was really looking forward to because that's my hometown, and we based the collection a lot on my personal style and the California style," she said of the first event. "That one was amazing, and now we are here in New York." And it was shaping up to be just as special—even before heading out, Gerber's hotel room was decorated with Mylar balloons in the shape of a cartoon in her likeness. "I never thought I'd have my little cartoon character on a balloon," she said, gesturing to the floating decoration. "This is like the best thing ever. We also have lollipops. And water. I don't know why I'm most excited to have my name on a water bottle. Like, yes." Here, the model talks about the new collection and working with Lagerfeld.

How did this collection first come to be?

Karl's team reached out, and when I heard about it, I didn't believe that anything would happen. I was like, "I can't believe he even remembers me. I've only worked with him a few times.'" This was about a year ago, and I thought there was no way this would actually happen. Then we started doing meetings, and after the first meeting, I was like, "They actually care what I have to say." Then to see it all come together, it has been really surreal.

When was the first time you met Karl?

The first time I met Karl was at a Fendi fitting. I didn't know he was going to be there; I didn't assume he was going to be as involved as he is with every collection that he does because he's so busy and does so many things. But he's there in every fitting. I walked out and saw him, and it kind of took my breath away. A warning would have been nice. He was like, "Hi, Kaia." I couldn't believe that he knew my name or knew who I was. It was awesome. I've gotten to shoot with him a couple of times, and it's always incredible. The list of things that he is a pro at is never-ending.

How was it designing clothes with him?

I just learned so much designing with him. I couldn't have asked for a better teacher. This is my first time ever designing anything, and to have Karl teach me was the most helpful person I could have ever asked for.

What did you go into this collaboration wanting to design?

I knew I wanted to stay really true to my home and my personal style and the relaxed L.A. vibe but also Karl's Parisienne-chic thing that he does incredibly. I wanted our two worlds to meet, and I think they meet in a really nice way. We wanted to incorporate both of our styles.

Did you ever disagree on anything?

We actually didn't. I expected there to be some because L.A. and Parisienne styles are so different, but we were both so focused on the classics of each style. I always dress in a leather jacket or something supersimple, and that's what he's so good at as well, so it ended up being really nice.

Do you find your style changes based on the city you're in?

One hundred percent. I definitely dress it down a lot more when I'm home in L.A., and then in Paris, I love a good blazer. I've definitely taken a lot from Parisienne style, and now I feel like both worlds are weaving no matter where I am.

What's your New York style like?

Well, this week the weather has been insane. But I'm happy we made a jacket, so I have this dress, but it's raining and I have a leather jacket to put on. It's very on the go, ready for whatever.

What was it like putting on something you designed for the first time?

It was crazy. Seeing it in front of me was the craziest thing because I never thought that I'd actually make something. I had all these ideas in my head, but I was like, "They'll never go anywhere." Seeing the first sample, I couldn't believe it.

Had you thought about designing before?

I have. I've always loved fashion, but I just really didn't know how you even begin or the process, so to learn the process along with Karl was the greatest. When I was little, I'd draw or go into my mom's closet and find dresses, but I had no idea what I was doing.

Have you started giving your friends pieces from the collection?

Oh my gosh, yes. That's the best part. Honestly, wearing it myself is really exciting, but seeing my friends and family wear it... I even have my grandma messaging me, like, "Kaia, I really need this piece." I just think it's the sweetest thing ever. That's why I did this—I wanted to see people wearing it and enjoying it and to make people happy.