The unit for the smallest detectable mouse movement is called a Mickey

Explanation

Named after Mickey Mouse, a mickey is a unit of measurement for the smallest detectable movement of a computer mouse. It is generally defined as 1/200th of an inch (approximately 0.13 millimeters), and mouse speed is sometimes expressed in mickeys per second. It is an informal, just-for-fun unit rather than an official one. Modern hardware specs instead describe sensitivity in DPI (dots per inch), where each individual "dot" or count of movement is essentially one mickey.