are given screen time for a brief, but recognizable, moment, such as Bing Crosby and Bob Hope momentarily appearing in a circus audience during The Greatest Show on Earth. They can be recognized, but sometimes are not credited for financial reasons – if they receive credit, they would be due payment commensurate with their fame. An example of this is James Cagney being clearly glimpsed during the opening scenes of MGM's Mutiny on the Bounty (1935) starring Charles Laughton and Clark Gable. Cagney was contracted to Warner Bros. at the time and was arguably their biggest star but appears briefly as an unbilled and presumably unpaid extra at the beginning of the rival studio's seagoing epic. Screenwriters billing Writing credits for films and TV shows written under the jurisdiction of the Writers Guild of America (WGA) use the WGA screenwriting credit system. For writers who belong to the WGA, the writing credits affect reputation, union membership, and income. Under the rules, the film producer must first submit the proposed writing credits for the project to both the WGA and all the participating writers. If any participating writer objects to the proposed credits, it then enters arbitration, with the WGA being the final arbiter. The WGA rules help dictate whether a screenplay should be classified as "original" or is instead based on another source. If based on another source, an additional "Based on a book/play/other source by" is generally required. In the case of a sequel to the film, the credited writers of the original motion picture may be entitled to a "Based on characters created by" credit. The WGA's rules also outlines when credits can be apportioned separately for the story, and for the screenplay itself when all writers were not equally involved in the creation of both. When the same writers are entitled to both "Screenplay by" and "Story by" credit, they will instead by listed under one "Written by" credit. For writing teams of two, they are credited as one, separated on the credits by an ampersand ("X & Y"). If each works independently on the script (the most common system), they are separated by an "and". If more than two persons worked on the screenplay, the credits may read something like "screenplay by X & Y and Z and W", where X and Y worked as a team, but Z and W worked separately. The WGA system