In The Hitchhiker’s Guide to the Galaxy, the perpetually depressed robot is Marvin.
Marvin is the Paranoid Android, a robot distinguished by severe pessimism, boredom, and a belief that his vast intelligence is wasted. In the 2005 film, he becomes involved with Arthur Dent, Ford Prefect, Trillian, and Zaphod Beeblebrox during their escape from Earth and their journey across the galaxy. Alan Rickman provides Marvin’s voice in the English version.
The character originated in Douglas Adams’s Hitchhiker’s Guide to the Galaxy stories, which began as a BBC radio comedy in 1978. Marvin’s full title is often given as Marvin the Paranoid Android. Arthur Dent is the human protagonist, Ford Prefect is his friend, and Zaphod is the two-headed former president of the galaxy, so all three are distinct from the robot.