Happy Birthday, Sia! Here’s 6 of the Singer’s Best Moments

December 18 is Sia's birthday, and we have to celebrate in style. Despite her mysterious stage presence, the singer and songwriter left a remarkable impression this past year in pop music. She has also raised social awareness for the LGBT community. Here are 6 of our favorite moments from the artist.

1. She dedicated "The Greatest" to the victims of the Pulse shooting.

Sia surprised fans when she released her latest single, "The Greatest," Labor Day weekend this year. The video included longtime collaborator, 13-year-old Maddie Ziegler, who had rainbow paint on her face and danced with 49 other dancers--one for each of the victims of the Pulse nightclub shooting in Orlando, Florida. The song is a powerful affirmation of solidarity with the LGBT community and a fitting tribute to those lost.

2. She had the best #ImWithHer post on Twitter.

The pop singer sampled from "The Greatest" again when Donald Trump mocked Hillary Clinton during a debate about Clinton's ability to perform as president and her "stamina." Sia burns Trump and supports Clinton in one fell swoop.

3. She slays every live performance.

When singing live, Sia is known for her signature two-toned wig with bangs covering her face. But that's not all she's known for. Put Sia on a stage and her voice will slay the house down.

4. And we mean every live performance, including in the car.

Sia joined the Carpool Karaoke alumni this year when she appeared with James Corden on the popular Late Late Show segment. She gave both an honest interview with the late-night host and a fun, lively rundown of her recent hits.

5. Even A-listers want to be her.

Flawless is hard to imitate, but in Sia's case, even top stars have tried. Ellen DeGeneres and Heidi Klum teamed up to spoof the artist by dressing up as Sia and Zeigler, respectively. Much as we love you, ladies, sometimes there's no beating the original.

6. If she didn't sing your favorite pop jam, she probably wrote it.

Before she crashed on the performing scene herself, Sia was (and still is) a prolific songwriter and has penned hits for Rihanna, Britney Spears, and more over the years.