The "blue pee" in The Madness of King George refers to a symptom of King George III's illness, linked by the play and some historians to the genetic blood disorder porphyria, which can cause blue urine and mental/physical symptoms like delirium, pain, and anxiety, though other theories point to bipolar disorder or arsenic poisoning from treatments like gentian, which also affects urine color, making the exact cause of his episodes debated but the blue urine a key dramatic and historical point.