I got called to write for Aerosmith, nothing ever came of it, but I ended up spending the day with Steven Tyler and going to his house and we sat down at the piano, just me and him, and he sang for me and played, then he asked me to sing for him, and then we sang harmony together. That was just a big moment where it was like 'oh my god, my life is crazy!' It was really cool.

A lot of people, Lady Gaga and Katy Perry and a lot of people have written for other people, and of course Bruno Mars. So I think it's a great way to break into the industry and show people what you can do and show them your talent and people tend to listen a little differently to your own music as an artist, when you've proven yourself as a good songwriter for other artists.

Sometimes I write a song and I'm down with it but I'm like yeah, whatever, and then everybody loves it and then it blows up. I'm like: "Okay! I didn't see that coming."

Obviously I love writing with Katy [Pery], I feel like we're the same person when we write together. Even though we fight a lot, we fight over every line and we pull each other's hair and we cat-fight all the time, it's always worth it in the end.

If you can take it to the next level and really tell an interesting story in a unique and fresh way, then I feel like that's a great song.

In my head, I wanted to be Madonna, but the music I was writing on paper was not what you'd choreograph dancers in costumes to. It was more coffee-house stuff.

I got called to write for Aerosmith, nothing ever came of it, but I ended up spending the day with Steven Tyler and going to his house and we sat down at the piano, just me and him, and he sang for me and played, then he asked me to sing for him, and then we sang harmony together. That was just a big moment where it was like 'oh my god, my life is crazy!' It was really cool.