Bottle episode

In episodic television, a bottle episode is produced inexpensively and restricted in scope to use as few non-regular cast members, effects, and sets as possible. Most bottle episodes are shot on sets already built for other episodes, frequently the main interior sets for a series, and consist largely of dialogue or scenes for which no special preparations are needed. They are also commonly used when a script has fallen through and another script has to be written on very short notice.