Reasonable look-alike actors were available for all of the characters except Danno, so James MacArthur played a dual role, except in the last scene, where his impersonator was played by Lowell Larson, a University of Hawaii engineering student.
It is revealed that McGarrett graduated from the United States Naval Academy.
James MacArthur's voice was dubbed when he was playing the role of his impersonator. At a 1996 convention he was asked about it, but said he could not recall who performed it.
The building used as the bogus Five-O headquarters is the Kapuaiwa Building in the Capital Historic District of Honolulu. It was constructed in 1884 for the purpose of a fireproof repository for government documents.
When they find the "fake" Five-0 headquarters, McGarrett tells Danny to check with BCI . This stands for Bureau of Criminal Investigation, and assists state and federal authorities in criminal investigations.