The 'Chandelier' hitmaker originally cast the 'Transformers' actor in the lead role of Zu in her upcoming movie, but had a change of heart after meeting with the 'Amost Famous' star.
Speaking with Australia's Studio 10, Shia revealed: "I was going to do a narrative film, and in fact, Shia LaBeouf was cast to play Kate's character.
"I asked for a meeting with her, and she said she was born to do it. She could sing, she could dance, she could do it all."
Sia re-cast the role with Kate because she "liked the tone of her voice".
She added: "I said, ‘Would you shave your head?’ and she said yes, and Bob’s your uncle.”
The movie has faced controversy because of the casting of Maddie Ziegler as an autistic girl who moves in with her newly-sober half-sibling Zu, despite the fact the 18-year-old star isn't autistic herself.
Sia recently defended the casting of her frequent collaborator, insisting it was more "compassionate" than hiring someone with autism.
She tweeted: "I did try. It felt more compassionate to use Maddie. That was my call...
"I cast thirteen neuroatypical people, three trans folk, and not as f****** prostitutes or drug addicts but s as doctors, nurses and singers. F****** sad nobody’s even seen the dang movie. My heart has always been in the right place.(sic)"
Meanwhile, the 45-year-old star recently claimed she was "conned into an adulterous relationship" with Shia.
The 'Cheap Thrills' hitmaker branded the 34-year-old actor - who appeared in the music video for her 2015 track 'Elastic Heart' - a "pathological liar" and urged others to "stay away" from him.
She wrote on Twitter: "I too have been hurt emotionally by Shia, a pathological liar, who conned me into an adulterous relationship claiming to be single. I believe he's very sick and have compassion for him AND his victims. Just know, if you love yourself - stay safe, stay away."
Sia's comments were made in support of FKA Twigs, who is currently suing Shia for sexual battery, assault, and infliction of emotional distress during the course of their brief relationship in 2019, claiming she was subjected to "relentless" abuse from him.
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