This episode marks the 200th episode of the series.
Chang Apana (1871-1933) was a real detective with the Honolulu Police Dept. for 34 years (1898-1932), working primarily in Chinatown. His exploits are legendary in law enforcement circles in Hawaii, including a story in which he singlehandedly apprehended 40 people in an illegal gambling hall, using only a bullwhip. Chang Apana was the inspiration of the fictional detective Charlie Chan.
McGarrett correctly notes that Chang Apana was the inspiration for Charlie Chan. A displayed photo of Apana is actually that of Warner Oland, the movies' most famous portrayer of Chan, taken from the film The Black Camel (1931).
This was Richard Herd's final television acting role before his death on May 26, 2020 at the age of 87.
When they go to talk to Mr. Pettifer, Steve's grandfather and his partner Milton are impressed that Pettifer had his newspaper "imported from the States", implying that the United States is a separate country. In 1941, it technically was; though Hawaii was an incorporated territory at the time, it wouldn't be recognized as a sovereign state until its admission to the union in 1959.