24 seasons and over 500 episodes in, the Simpsons has established itself in the domain of pop culture for good, regardless of where and when you believe the show began a downward trend in quality. One thing that has kept it alive this long is that in lieu of writing stories focused on the central Simpson family or even the supporting cast, the show has become a sort of guest-star mill, featuring whatever flavor-of-the-week celebrity will agree to appear on the show.
That means a lot of musicians have shown up on there as well. In fact, the Simpsons has long been renowned for featuring some of the greatest musicians of all time in some of the greatest scenes in the show's history. All three Beatles and Michael Jackson have shown up in the past to wide critical acclaim.
But in recent years, music has become sort of a blight on the show. In ratings-grab stunt-casting, the show has featured some awful musician cameos that have embarrassed all parties involved. These are the five worst the series has ever featured.