In the late 1980s, Stan Lee had considered a film/TV series about Shang-Chi and had in mind Brandon Lee, son of martial arts superstar Bruce Lee, for the role. Shang-Chi was visually based on Bruce Lee so Brandon seemed a fitting choice, but the plan fell through.
(at around 30 mins) One of the lower tier fights in Xialing's fight club had a fight between one of the Widows who appeared in Black Widow (2021) and a fighter enhanced with the extremis treatment from Iron Man 3 (2013).
Destin Daniel Cretton said they went through a lot of contenders for the lead role but found the perfect package in Simu Liu. He has the athletic abilities, but he's also a terrific actor, showed fantastic chemistry with Awkwafina, is fluent in English and Mandarin and is comfortable shifting between Western and Eastern cultures. Co-writer Dave Callaham adds that Liu's "code switching" ability was an integral element to the character of Shang-Chi as well.
Simu Liu, when cast as Shang-Chi, was knowledgeable in taekwondo, gymnastics, and Wing Chun. For his role as the Master of Kung Fu, Liu trained in tai chi, wushu, Muay Thai, pencak silat, Krav Maga, jiu-jitsu, boxing, and street fighting.
This is renowned Hong Kong film actor Tony Leung Chiu-wai's first role in an American film and his first English-speaking role, even though he has always spoken it fluently.