While engaged in Anal sex on a beach the man pulls his penis out of the girls ass rubs it in the sand and shoves it back in her ass.

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.