Cave Johnson is the founder of Aperture Science, which was a company that produced shower curtains before delving in science. The labs of his company are the settings for both Portal and Portal 2. In Portal, he goes unseen and unheard, but he was fleshed out in other sources. He is heard through pre-recorded messages in Portal 2, when Chell goes through an abandoned section of the Aperture Laboratories.
He switched his company from shower curtains to science, employing a lot of top-notch scientists. His ideas were wild and quite dangerous, such as replacing a person's blood with gasoline. Eventually, his company would create a portal device, although not the portable kind seen in the game. This device was not ready for the real world and was repeatedly delayed thanks to Johnson's distractions.
Eventually, the company would start losing money in the 1970s, due to the rise of Black Mesa, a company featured in Half-Life. Johnson became desperate for more test subjects, pulling people from the streets even. Due to an experiment in which he tried to refine moon rocks, which became toxic, he became very ill.
During the 1980s, as technology advanced, he began researching on how to preserve his brain by inserting his intelligence into a computer. He had a feeling this wouldn't be finished before he died, so left instructions to appoint Caroline, his secretary, as the head of the company. He also wanted her brain to be placed into a computer, which was eventually done, giving birth to GlaDOS.
