quality
This term is properly spelled "QUALITY" (without the quotes), in ALL CAPS. This tag is written in lowercase due to limitations in Danbooru's tagging system.
The term "QUALITY" indicates (with ironic intent) glaring yet humorous errors and flaws in commercial works of poor quality or works of otherwise good quality. This can be caused by poor budgeting (blowing most of the budget of an anime into the first episodes, per example), a small budget or outsourcing to cheaper studios, although it can also be as a result of a honest mistake.
The Japanese equivalent is "ヤシガニ" ("Coconut crab"), a reference to Lost Universe's 4th episode which, due to the show's notoriously bad animation, was turned into a byword for bad animation in general. A more descriptive term is "作画崩壊" ("Animation collapse").
This tag can be applied to any posts that intentionally recreates the disfigured art or animation frame for humorous purposes. Do not apply this tag to any other post with generally poor quality otherwise. For posts featuring an error unintentionally created by an artist, see artistic error.