The term “bottle episode” is used in episodic television, where episodes are produced using existing resources or using whatever money is left over, typically using already existing sets or sometimes limiting the scenes or recaps. No special preparations or sets are built, these bottle episodes are shot on already built sets. The Bottle episodes are “make or break” process as they can be best or worst episodes in the series. They are season openers and closers. The cast are made to stay in same location.
Bottle episodes are not filler episodes, they are the episodes where actors sometimes give in their best performance. The producers instead of spending the money evenly over the episodes spend towards the start, middle and end of the season. In the bottle episodes, regular cast, set in the single location or sometimes even entirely in one room is preferred. This way production costs are reduced as there is no need to scout locations, build new sets, or create fancy CGI graphics. This doesn’t mean the episode is cheap, like any regular episode unforeseen complications can cause the show to run over the scheduled budget.
The term “bottle episode” originated from the Star Trek series when the crew called these episodes “ship-in-a-bottle” episodes as the series took place on board the “Starship Enterprise” and these episodes are also called “bottleneck episodes” because money has to pass through a bottle neck (referring to constricted budget). Bottle episodes are known as a challenge or a chore depending on the writer, with writers focusing on making the episode stronger. Bottle episodes are perfect for a plot and character development to grab the audience attention to keep them entertained.
The producers spend more money on particular episodes to make it a memorable and distinctive one such as finales and opening ceremonies. The guest appearances are uncommon and writer focuses solely on familiar characters of the show. Yet bottle episodes can be aesthetically and structurally pleasing, as they offer creators a chance to work with their core characters. It became a brilliant way to keep the episodes fresh and flawless. The bottle episodes are shot on sets where main interior sets of the series are already built and they consist largely of dialog and scenes where there is no need for special preparations.