The man Smart is following at the beginning of the episode and who later is identified as KAOS agent 'Number 3' was played by Robert Ito who is possibly best known for his role in Quincy M.E. (1976) as Sam Fujiyama. He was not credited.
Last appearance for The Claw/The Craw. Leonard Strong appeared as a different character, Lin Chan, in The Laser Blazer (1968).
The character in the title is a parody of Charlie Chan, a fictional Chinese-American detective created by Earl Derr Biggers in 1923 and was used in a movie series in the 1930's and 1940's.
Joey Forman was a comedian who played the brilliant Asian Detective Hoo. Unlike other more offensive portrayals, Forman's clothing and Asiatic makeup was made in the same vein as that of Charles Laughton for realism. The term "Asian" wasn't an acceptable term for Chinese, Japanese or any non-Polynesian nationality for another 25-years. Oriental was a term of respect when Japanese or Chinese were global terms in the Post-WWII, contemporary (1966) Vietnam War time frame.