Douglas Englehart, a professor at Stanford University, developed the mouse in 1964. It was to be used with a five key chorded keyboard meant to replace the typical typewriter keyboard. The mouse was called a mouse because it resempled one. The two buttons were eyes, and the chord was a tail.
The mouse was never used until 1983 when it was introduced on the Apple Lisa computor.
He also invented a foot operated 'rat', but that was never produced.