On the Katy Perry episode of Carpool Karaoke, James Corden asked her about the inspiration for this song—in particular a rumour that Scarlett Johansson is the person meant in this song, to which Katy responded:

That song was kinda… I meant, she’s definitely one of my muses inspiring it, but it was actually about a girl that I met when I moved [to Los Angeles] at 17.

Furthermore, Katy said that she never kissed the girl this song is about or Scarlett Johansson, but kissed other girls and is down to kiss Johansson, too.

The chorus actually popped into my head when I woke up. It was one of those moments where you hear artists talking about songs they get in dreams or in the middle of the night. I was like wow what an interesting subject matter to kind of pop into the head and I didn’t do anything with it for about a year and a half. Then all of a sudden at the very end of making my album. I literally had two days left in the recording studio with my producer Dr. Luke. We just said we’re going to finish it. it’s so catchy because it won’t get out of our heads."

–via GoogleBooks (2008)

We’ve really changed, conversationally, in the past 10 years. We’ve come a long way. Bisexuality wasn’t as talked about back then, or any type of fluidity. If I had to write that song again, I probably would make an edit on it. Lyrically, it has a couple of stereotypes in it.

–via Billboard (2018)