Johnny 5 is the robot from the highly successful 1986 movie Short Circuit and the rather less successful sequel.
After escaping from the laboratory, Johnny is eventually discovered by Stephanie Speck who attempts to educate him in the ways of humanity. Much of the story involves Johnny's attempts to avoid being captured and taken back to the lab or destroyed. His creators are understandably keen to have him back since not only is he expensive but he's also equipped with lethal weaponary in the form of a laser cannon.
As with many robot stories, Short Circuit contains elements of the Frankenstein and Pinochio tales. Both these are referenced directly in Short Circuit 2 where Johnny is seen reading the books.
One of the reasons for the popularity of both the movie Short Circuit and Johnny 5 himself is undoubtedly the design of the robot. It manages to be a clearly artificial, mechanical construct yet one which we can believe really has become alive in an almost childlike fashion.
In other words: he's cute.