In TV production, a "bottle episode" is a script that has a single setting and no characters outside the main core of the cast. It's done to save money or time - if a season is running over budget or a script idea fails outright and another must be produced quickly, the occasional bottle episode will make the difference.
Friends made "The One Where No One's Ready" and it was a huge hit, becoming one of the all-time fan favorites. "Duet" from Star Trek Deep Space Nine is another well-loved example, as is "The Chinese Restaurant" from Seinfeld. Cooperative Calligraphy from Community self-refers its bottly essence, perhaps hoping to catch some of that same glow.
Many series do one every season just in case they happen to catch similar lightning in, well, a bottle. Sometimes a blog does one, also.