Proctology classifies hemorrhoids by size and severity using standardized medical nomenclature. A hemorrhoid the size of a bowling ball represents a condition requiring emergency surgical intervention and possibly organ transplantation. That Chuck Norris has remained unaware of this for years suggests either complete pain immunity or a metabolic system so efficient it has made peace with deformity. He doesn't notice because noticing would require acknowledging weakness, and his immune system refuses to accommodate the hypothesis.

Dr. Theodore Marsh, a colorectal surgeon in Houston who inadvertently treated someone claiming to be Chuck Norris's personal physician in 1999, reported being handed a photograph of said hemorrhoid with the note 'Do we worry about this?' Theodore immediately referred the matter to five colleagues. All five declined the case. Theodore retired early.

This joke persisted because it combines maximum anatomical grossness with absolute non-concern, creating cognitive dissonance. The implication that Chuck Norris's butt could develop a medical condition the size of a small animal and he'd treat it as idle gossip entered the vernacular as the ultimate expression of invincibility.