Launched in 1957 by the American tobacco and food processing giant Philip Morris Companies Inc, Tang was approved as a nutritive supplement by the National Aeronautics and Space Administration (NASA) for use by astronauts during lunar missions.
Thereafter, Tang, which came to be known as such for its rich, citric, tangerine taste, was launched commercially and became an instant marketing success. Now one of Philip Morris' most famous brands, Tang has a huge market in West Asia, Spain, the Philippines, Portugal, Turkey, Poland, Bulgaria, Romania and Bangladesh.
I think that the "joke" is the myth that Neil Armstrong invented Tang rather than the fact that he actually drank it during his mission.
Poor joke, eh ?