Screenplay equivalent to fanfic, fanfiction. Any screenplay adaptation created by an amateur. Fanscripts are often created when a film adaptation of a beloved book/play/story is poorly received by fans, and a fanfic writer wants to show an alternate and (in their opinion) superior film version of the material. Presenting it in script form is the closest thing to shooting an actual film.
The film adaptations of Harry Potter and Weber's The Phantom of the Opera have "inspired" a few fanscripts.