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This is a classic money-saving technique producers use when they've gone over-budget in the middle of a season. Bottle episodes usually contain no guest stars and the action takes place almost entirely on an existing set. Community lampooned the trope in Season 2's "Cooperative Calligraphy," when no one could leave the study room until Annie's missing pen was found. Yes, the set-ups are often silly and transparent, but when done right — Friends' "The One Where No One's Ready", and Breaking Bad's "Fly," for example — the episodes can actually become rather memorable.