David Carradine had no formal martial arts training of any sort. He had received some training as a dancer when he was younger. This was a particularly aggravating fact for Bruce Lee after he was turned down for the part of Caine.
The set for the Shaolin Temple was originally a set used for Camelot (1967) that was inexpensively and effectively converted for the Chinese setting.
In several episodes, a younger Kwai Chang Caine was played by Keith Carradine, David Carradine's younger brother. Their other brother Robert Carradine and their father John Carradine also appeared in episodes (as Sonny Jim and Serenity Johnson, respectively).
When Warner Brothers was developing this with Bruce Lee, it was known as "The Warrior". That original series concept would be finally be produced decades later as the TV series, Warrior (2019), for Cinemax.
According to Bruce Lee's widow, Linda Lee Cadwell, Lee originated the concept, and was intended to star in the series, but David Carradine was cast because the network felt the American audience was not ready for an Asian actor as the lead, and Lee received no credit for his concept (this was dramatized in Dragon: The Bruce Lee Story (1993)). However, according to the producers, although Lee was consulted and was considered for the role, they created the concept and Carradine was always their first choice.