The show poked fun at several fashion trends that are probably lost on the modern day audience. Rockford jokes about parachute pants, which were were very popular in the late 1970's and were in fact made from the same material as parachutes.
The gangster talks about somebody killing 19 people and getting rich by his story. He's talking about the infamous Son of Sam. The revelation that he sold his story to a book publisher led to numerous laws that didn't allow perpetrators of heinous crimes to profit from their actions.
Jim is taken from his trailer to a remote building by two hoods to be killed. The hoods are distracted by rats and Jim jumps out a window, shot in the rear as he goes out. James Garner was wounded in the Korean War, shot in the rear by "friendly" fire.
The Nehru jacket was a popular fashion item that hipsters wore in the 1960's after becoming famous by its use by Pandit Nehru, the former Prime Minister of India. The joke here is that not only does Rockford have one in his closet (something that is completely out of character for a hard boiled detective), but that he still has it, even though it went out of fashion ten years before.
When being hired by Masters (played by 'Rene Auberjonois'), Jim hesitates, but then quotes his rate as "$250 per day, plus expenses," which is higher than his heretofore typically quoted rate of "$200 per day, plus expenses."