Someone (usually a black guy) who hangs around the subway turnstiles pretending to "check the balance" on his blank Metrocard that he probably found in the garbage-uses this as an excuse to loiter near the turnstiles-asks everyone who comes along if they can help him out with whatever

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.