The episode begins with a surprise birthday party for McGarrett, very sweetly and lovingly put together by the staff, governor and Steve's fellow coworkers on the five-O force. The episode aired on December 31, 1969. Jack Lord celebrated his 49th birthday on December 30th, 1969.
While in hospital, McGarrett asks the telephone operator to dial 732-5577---the telephone number of Five-O's office. That number was actually the number for Hawaii Five-O Studios on Diamond Head Road in Honolulu.
During the investigation, Che discovers that Masterson used a part from a German car called a 'Westphalia Oberland" to construct the bomb used on Steve's car. Danny later finds out that there is only one dealer on the island. They actually go to a Volkswagen dealership.