Zaphod Beeblebrox is from the fifth planet of Betelgeuse.
He is a "semi-cousin" of Ford Prefect, with whom he "shares three of the same mothers". Due to "an accident with a contraceptive and a time machine", his direct ancestors from his father are also his direct descendants.
Zaphod has two heads, three arms and is "clever, imaginative, irresponsible, untrustworthy, extrovert, nothing you couldn't have guessed". He was also briefly President of the Galaxy. His responsibility in that position was to draw attention away from the true rulers of the universe. To that end, Zaphod and his outrageous behavior were highly successful. And he is the only man to have survived the Total Perspective Vortex (albeit in an electronically synthesized universe which was created especially for him). He used his position as President of the Galaxy to steal the Heart of Gold, a spaceship taking advantage of Infinite Improbability Drive, at its unveiling. He is also the inventor of the Pan Galactic Gargle Blaster, and is the only person alive who can drink more than three in a single sitting.
In the first book, he mentions that his third arm was added on to help with his ski-boxing. In the radio show it seems that the third arm is part of his species that has an opt in policy, since he grows it back for Trillian. In the movie, Zaphod states that the second head is the result of carving in his brain. In the books Zaphod did this to conceal his true reason for running for President, a major scheme which makes us the majority of the second book and follows into others. While other media have claimed his head was always there (the Text Adventure Game, also written by Douglas Adams claimed that Arthur only did not see it at the party they met was that it was a fancy dress party and Zaphod had disguised his second head as a parrot so as to complete his pirate costume), the movie states it was the result of the carving, which had been done because Beeblebrox did not think "anyone can be President with a full brain."
Zaphod has a successful business in secondhand biros. This may be due to his discovery of a planet where biros escape to to live a nice biroey life. If so he employed a man to sit on this now empty planet denying the whole thing.
Left Brain Edit
In the semi-official Eoin Colfer novel And Another Thing... Zaphod has his second head (apparently the more intelligent one) detached and functioning as the Heart of Gold computer, replacing Eddie. This leaves the still attached Zaphod a little slower witted but it is noted that Left Brain being in charge of the ship has decreased the amount of accidents that would have been caused by Eddie. Left Brain and Zaphod develop a semi-antagonistic relationship despite still working with each other. At the end of the novel they are both working on Zaphod's presidential re-election campaign. Ford was also able to freeze Left Brain in a logic debate over the improbability of the Heart of Gold saving him and Arthur from doom near Earth twice after the ship saves them from the Grebulon's death beams.