"My mum and I went for a walk in Sydney. We were, like, across the street from the hotel and the crosswalk is this little… you press it and it's like 'doop, doop,'" she revealed in the interview. "And I was like, 'That's hard!' That's the sound that it makes when you have to wait."
We ALL know the sound she is talking about.
Billie saved the sound in her phone as 'Grart', and later, she and her brother Finneas incorporated it into the song.
"The hilarious part about all this is we were just in Australia in May and my dad goes, 'Have you heard these crosswalks?'" Finneas explained.
"And I was, like, 'Yeah, it's the chorus in 'Bad Guy''. And he goes, 'What?' I was, like, 'Yeah … never mind man.'"
The song won Song of The Year at the Grammy Awards, also topping the Triple J Hot 100 over Australia Day weekend.
It marks Billie as the first female solo artist to win it!