1) Bit part 2) Cameo role, typically 3) Small part in a play 
[sport term] This category contains articles related to spaceflight events and launches in 1980. ...[sports] The term walk-on is used in sports, particularly American college athletics, to describe an athlete who becomes part of a team without being actively recruited beforehand or awarded an athletic scholarship. This results in the differentiation between `walk-on` players and `scholarship` players. ==College football== Walk-ons have a ...
A small part of short duration in a motion picture; the role usually does not call for dialogue. Often production companies will offer bit-parts/walk-on parts to significant actresses and actors for their audience appeal. The outcome is usually surprising and/or humorous. (Also see `cameo` and `bit`.)
(or Walk-through) The act of entering a scene, making a strong offer that advances the scene, and then exiting. Use sparingly.
[n] - plays a small part in a dramatic production
noun plays a small part in a dramatic production