The Magical Negro is a type of character that appears in mostly American literature and cinema. They are always a background character who have unusual skills, exceptional insight, and/or mystical or magical powers. Their role is to assist the protagonist (who is white or Caucasian), appearing when their need is dire, acting like the Mentor or Threshold Guardian archetypes in the Hero's Journey.
The term purposely uses throwback language because it highlights racial stereotyping from old stories like Sambo. Director Spike Lee used it in a speech when discussing the continued use of the stereotype in the twenty first century. The concept is popular in fiction and movies, almost becoming a trope when used in the suspension of disbelief.
Examples include:
Iron Noder 2017