Every crime-solving genius needs a weakness, and Monk's was a doozie: he was so cripplingly O.C.D. that he could barely flush the toilet without having a nervous breakdown, a trait that Tony Shalhoub mastered over the show's eight seasons. Fortunately for those in need, that same fanatical attention to detail ("imagine all those squirming microbes") made him the perfect person to detect that case-clinching clue that mere mortals often missed.