Film And Theatre Styles (or Genre Option, and later Film, TV And Theatre Styles) was a game played on both the British and American editions of Whose Line.
The game began with the audience being asked to name their favourite styles of film and theatre acting (while television was only added to the game name later, television styles were present from the earliest times). The pair of performers were then given a scene, during which they would be asked to adopt some of these different styles.
Many different pairs (and, by the American edition, trios) were tried, however the most well-known was Ryan Stiles and Colin Mochrie. Perhaps their most famous style was "Shakespeare", which traditionally involved Ryan declaiming nonsense - two such lines being "If I were a man with gills I would be a fish" and "the sky, the sky beyond the door is blue" (to which Colin responded "Aye, 'tis blue" before Clive Anderson buzzed for a style change with the comment "That's the worst Shakespeare I've ever heard").
The game was also responsible for many of the early impressions on Whose Line, such as Greg Proops' Woody Allen.
This game also came the closest to nudity in Whose Line history. Stephen Fry and Peter Cook were told to perform part of a scene in the style of "British Farce", which resulted in Stephen pulling his trousers down.