Wonko the Sane, marine biologist and scientist; real name John Watson.
Wonko / Watson lived in California with his wife. More specifically, the pair lived in a curious place called 'the Outside of the Asylum'. To explain: One day, after coming across a set of detailed instructions on a set of toothpicks, Watson, distressed and fearing for the world's sanity, built 'The Asylum' to put it in and help it get better. The Asylum is a four-walled house turned inside out. That which one would be inclined to take as the door into the house opens into a lawn with benches and walking paths. This is the area that Watson calls Outside the Asylum. Thus, the inside of the asylum contains the entire world, save for that small area. Within that small 'outside' area, Watson has mounted the instructions for the toothpicks, in order to discourage himself and others from going back into the asylum, i.e. returning to the mad world.
John calls himself 'Wonko' in order to remind himself that a scientist must be like a child in having no pre-assumed notions - 'Wonko' being a childhood nickname bestowed by his mother. Wonko added the epithet 'the Sane' to his name in order to reassure people of his sanity (!). That sanity was called into question frequently, not least because of Wonko's repeated insistence that he was visited by green-winged angels on scooters (angles later revealed to be the guardians of God's Final Message to Creation).
Arthur and Fenchurch visit Wonko in the fourth Hitchhiker's novel. Wonko explains to them the meaning of the mysterious glass fishbowls.