Failsubs, also known as LOLFansubs refers to translation errors, subtitle jokes or humorous subtitle animations made by amateur anime translators. These have inspired jokes including but not limited to descripted noises, engrish or funny translator side notes.
Fansubbed anime (and by extension, failsubs) began surfacing in the Western world in the 1980's, when anime was starting to boom. Enthusiasts with some proficiency in the Japanese language began to subtitle anime that hadn't been subbed officially yet so that they could share them with non-Japanese speaking fans. These fansubs were done mostly on VHS/Betamax, were terribly expensive to produce, and were of notoriously low quality.
The point of having a 'Translator's note' is to explain cultural differences between Japanese and western audiences, or to try to explain confusing scenes. Some amateur fansubbers will use the opportunity to editorialize about the scene.
Some subbers tend to use the translator's note as a sort of pop-up dictionary, leading to fansub memes such as Just According to Keikaku." Certain translator's notes are so long, they can even screen the scene with information, whereas, on the opposite end of the spectrum, there are some that just reveal how out of their depth the fansubbers are.
"I have no idea what s/he said here"
Not all fansubbers are fluent in Japanese. There are some instances where they don't even know what the scene is depicting. As a result, they will admit that they don't know what was said by the characters. These occur most often in characters who become very excited, and talk rapidly.
Fansubbers will occasionally put emoticons in their subtitles for their (and often the audience's) humor.
People Die If They Are Killed
"People Die If They Are Killed" is one of the most well-known Failsubs taken from the anime version of Fate/Stay Night. In this anime, the main character Shirou wonders why he survived even with the most gruesome and painful of wounds. Upon realizing has the 'Avalon' inside him, he thinks that it's morally wrong to be immortal, which leads to him saying the phrase.
All According to Keikaku
Am I kawaii, Uguu~! | Translator's note: Kawaii means cute
"Am I Kawaii" is a recurring image that is notable as a failsub as it has a redundancy similar to "Just According to Keikaku." While it's more related to the QUALITY meme, this failsub originated from the anime Kanon (See also: ~Uguu), and can be seen in the original What's All This Racket? rage comic.
DO NOT WANT
"Do Not Want" is a quote from a bootleg version of the movie "Star Wars Episode III: Revenge of the Sith", where Chinese subtitles directly translated the from the Chinese version rather than transcribing it from the original (English) movie.