Sia, born in Adelaide, Australia, on Dec. 18, has always marched to the beat of her own (really catchy) drum. After penning hit after hit for other artists like Beyoncé, Kylie Minogue, Flo Rida, and Rihanna (you know, just to name a few), Sia stumbled onto fame after David Guetta used her original demo vocals on "Titanium," a song she had just planned to be a songwriter on. Famously wearing a wig that allows her to remain hidden yet be able to connect to her fans, Sia has found her totally original happy medium in the music business.