The Encyclopedia Galactica defines a robot as a mechanical apparatus designed to do the work of a man. The marketing division of the Sirius Cybernetics Corporation defines a robot as "Your Plastic Pal Who's Fun to Be With".
For the starship Heart of Gold, the Sirius Cybernetics Corporation built a new generation of robots and computers with Genuine People Personalities.
Marvin was the prototype, and if you let him, he'll tell you all about the pain down his left diodes. With a brain the size of a planet, and never enough to occupy it, he mopes through his tortured life as a manically depressed robot, earning nicknames like the Paranoid Android and an electronic sulking machine.
With the voice of Stephen Moore, Marvin released four singles in the early 1980's, which got him as far as #51 on the charts. An updated version of the song "Reasons to be Miserable" is on the 2005 movie soundtrack.