The magical negro

http://en.wikipedia.org/wiki/Magical_negro

The magical negro is typically but not always "in some way outwardly or inwardly disabled, either by discrimination, disability or social constraint," often a janitor or prisoner.

The magical negro serves as a plot device to help the protagonist get out of trouble, typically through helping the white character recognize his own faults and overcome them.

Although he has magical powers, his "magic is ostensibly directed toward helping and enlightening a white male character." Although from a certain perspective the character may seem to be showing blacks in a positive light, he is still ultimately subordinate to whites. He is also regarded as an exception, allowing white America to "like individual black people but not black culture."

To save the white protagonist, however, he would do anything, including sacrificing himself, as Sidney Poitier portrays in The Defiant Ones, the prototypical magical Negro movie.‏² Note that Poitier's character is also saved by the white protagonist, as the two help each other throughout the film.

That Magical Negro All Over Again