What are filler episodes? I've heard people mention them a lot but I'm not quite sure what they are. Apparently Naruto is packed with tons of them, so what are they?
A simple answer taken from the internet.
A filler arc is a storyline (often, though not always, shorter than the regular arcs) in which, over a number of episodes, an adventure is detailed that is unrelated, or tangential, to the main story arc(s); often, the filler arc adventure does not derive from the original source material.
For example, there are plenty of filler episodes after Naruto defeated Pain. Most of the fillers are the story of a side character, or childhood flashback of a character.
Filler episodes are entries in a generally continuous serial that are unrelated to the main plot, don't significantly alter the relations between the characters, and generally serve only to take up space. This could be considered Padding applied to a whole franchise.
They are extremely common in Anime, where many shows have 26 or more episodes per season. The producers have to use filler just to meet contractual demands. [...] Sometimes entire filler Arcs are created, most often because the series Overtook the Manga. Just about every long-running manga-based anime action series will have gargantuan amounts of filler over time. This is because Japanese networks, unlike western ones, don't do reruns or season breaks. This is compounded when they go beyond the 26 episode mark. Many series air over 40 episodes per year, when they would have a hard time making even half of them related to the main plot.
From tvtropes: http://tvtropes.org/pmwiki/pmwiki.php/Main/Filler
While TVTropes does a good job of generally explaining what it is - that is, it's content which doesn't necessarily drive the overarching plot of the series forward - it may be good to look at why it comes about, specifically in series like Naruto or Bleach, and not in smaller series like Outlaw Star or Cowboy Bebop.
The executive summary:
In dual-published media (both anime and manga), filler is necessary to allow the source media (typically manga) to establish canon and story, while the adaptation media (typically anime) exists to mostly reflect the source media.
(Note that there are exceptions to this, such as cases in which the anime and manga are completely different works - notably in the case of Love, Chunibyo and Other Delusions - in that instance, we would treat these as distinct works, each in their own canon separate from one another.)
A lot of major anime series have a simultaneously running manga series to back it. This is true in the case of series like One Piece and Fairy Tail, which have a lot of volumes currently being published, and the story isn't yet complete. In the case that the story is still being told, one of two things have to happen to facilitate the need for filler:
- The anime runs into a scenario in which the story it's told is at a similar point to the manga, or
- The directors intentionally carve out some time for filler to ensure a smoother spacing of storyline, or to allow the manga to gain more story to animate.
The second scenario happens less frequently, but there have been times that I've observed in Naruto that filler was still being produced when it wasn't wholly necessary.
In the case of both Bleach and Naruto, it would come to pass that the anime would invariably catch up with the manga. In doing that, the anime can't realistically continue until new story is written. So, for a cour or two (or even an episode), the directors of the series would create a new storyline based in the same universe, which may or may not be entirely canonical. This is done to ensure that the anime continues during its allocated cour.
In the case in which the anime precedes the manga, I would presume that the storyline is well-fleshed out, and the manga drives to follow the anime, thus completely eradicating the concept of filler in manga backed by an anime.
This may still happen exclusively in manga though, especially if it's not airing anymore or has never aired; in the case of Hayate the Combat Butler, since it's stopped airing (and the airings didn't entirely follow the manga anyway), it has had filler chapters such as:
Kyoto and Ise - Conclusion (Night 3): This is supposed to be Night 3, but this is the 400th chapter so let's celebrate! Seriously