A script doctor, also called a script consultant, is a writer or playwright hired by a film, television or theatre production to rewrite an existing script or polish specific aspects of it, including structure, characterization, dialogue, pacing, themes and other elements.
Script doctors generally do their work uncredited, for a variety of commercial and artistic reasons. They are usually brought in for scripts that have been almost "green-lit," during the development and pre-production phases of a film, to address specific issues with the script, as identified by the financiers, production team, and cast.
Under the Writers Guild of America screenwriting credit system, a screenwriter must contribute more than 50 percent of an original screenplay or 33 percent of an adaptation to receive credit. Uncredited screenwriters are not eligible to win the Academy Award or the Writers Guild of America Award.