Joel Little has been in the studio with a galaxy of stars over the past seven years. The New Zealand-based producer has written and produced hits for everyone from Lorde ("Royals," "Yellow Flicker Beat") to Ellie Goulding ("The Greatest") and Khalid ("Young Dumb & Broke"), among many others.

But it was a chance meeting at a show by another act he's long been associated with -- New Zealand sibling due Broods -- that landed him on the song that currently resides at No. 2 on the Billboard Hot 100: Taylor Swift's "Me!"

In an exclusive interview with Billboard, Little says after he met Swift at that Broods show in Los Angeles they ended up hanging out when she was in New Zealand on tour last year.

"I have this amazing photo of my daughter in tears of joy meeting her backstage at the concert," he tells Billboard by email. "Once we got to know each other a little I think we realized we could probably write some good songs together, and a few weeks later she asked me to come to New York to work." The rest, of course, you can hear on the exploding pop bubble that is "Me!," Swift's hit collaboration with Panic! at the Disco's Brendon Urie.

Below, Little also talks about what excited him about working with Swift, the origins of "Me!" and how touched he is by the Swifties' embrace of the tune.

What excited you about working with Taylor?

First of all, I’m just a massive fan of hers, I think she’s a genuine songwriting genius and she’ll go down as one of the most iconic pop stars of all time. She’s in that upper echelon, where getting to work with her is like the holy grail for pretty much every pop songwriter. I was absolutely shitting myself before our first session, but it went great. We just clicked creatively right away and it was so easy, like we’d been writing together for years. I couldn’t believe it.

What was the genesis of the song? What ideas/lyrics did you start with and how did it develop?

We were actually finishing up another idea at the time. I think I was tidying up some vocals and she just sat down at the piano and started quietly playing an early version of the chorus. I remember turning around and saying, "What’s that?" and her saying something like, "Just this little idea I came up with in the car." So we quickly started building things from there.

How did she describe what she was looking for? What ideas did that spark for you?

She wanted it to have a bit of a classic throwback thing to it, with horns and organic elements mixed with modern production. The chorus melody has this huge celebratory feel to it that immediately made me think of 1960s big bands, so I wanted to incorporate a bit of that world in with all the other stuff I like to do. It was also important to her that the song didn’t take itself too seriously, that we kept it tongue-in-cheek and just let it be a fun, feel-good tune.

You’ve worked with so many iconic pop acts, but is there something next-level about trying to come up with a fresh sound for someone like Taylor?

Oh, totally. A lot of my success in the past has been with helping new artists figure out their sound, like with Lorde and Khalid early on before they became huge. Working with an artist like Taylor, who already has so many bonafide classic songs, was definitely a bit of a "mom's spaghetti" moment for me, just like, "Don’t fuck this up, man." But she’s so good at what she does that you just step your game up, too. Once we started working together and found out that we really complement each other with the way we do things, it just became super fun and inspiring and easy.

What’s your feeling about the audience reaction to the song?

It’s been totally nuts watching it all unfold, just crazy. Her fans are some of the most committed and passionate people in the world and I’ve loved watching all the reaction videos and the covers and the people singing along in their cars. The other day, I came across a video of this little kid sick in the hospital grooving along to it, which was really special. The main purpose of a song like this is just to try and brighten up people's day, so it’s nice to know it’s working.