Australian singer Sia enjoyed huge success with "Titanium" upon its release in 2011 and became a household name in the subsequent years with songs including "Chandelier" and "Cheap Thrills".
While "Titanium" has become synonymous with the 44-year-old's unique voice, Katy admitted during a recent interview that she was actually offered the song to record herself.
"I remember specifically listening to it on the plane, I was like, 'Oh my god, this song is so good. Who is the person on the record? They should stay on the freakin' record. This is a hit record; don't put me on the record! Keep Sia on this record!' " Katy smiled.
The "Roar" star added that she "wrote David an email back" which read, "You're crazy. I don't need to be on this record. Keep Sia on the record."
"And there is Titanium," she concluded.
Since then, the pair have worked together themselves - collaborating on several tracks including the 2017 hit "Chained to the Rhythm", from Katy's album "Witness".