Play on the words 'yaoi' and 'retard'. It's a usually-derogatory term used to denote someone who has an obsessive or blind fixation on yaoi, whether or not the pairing in question is even probable. Yaoitards are usually n00bs, too.

A phrase to describe someone who is cognitively degenerating. Synonym of "going off the deep end". Can have varying degrees of severity.

Reference to the song "Hey You" by Pink Floyd. The line "and the worms ate into his brain" makes no sense in an otherwise linear and literal narration throughout the lyrics.