Various celebrities and historical figures are kept alive as heads in jars of liquids. The technology is crucial to Futurama ' s connection with 20th- and 21st-century culture since it allows significant figures from the past to make appearances in the series. This also allows for contemporary celebrities to make guest appearances as themselves. The technology was invented by Ron Popeil, himself a head. People seem to be able to be resurrected using this technology, as every U.S. president is found in the "Head Museum"; the most prominent head is that of Richard Nixon who becomes the President of Earth. In " All the Presidents' Heads ", it is revealed the water they are kept in when drunk can send a person back to the year when they were the most famous.