With over seven hundred episodes, The Simpsons is full of minor characters who disappeared after only one appearance. However, there's one character who, after appearing in one of the show's darkest episode, has remained controversial: Frank Grimes.
Played by series mainstay Hank Azaria, Grimes' only starring role was in The Simpsons Season 8's "Homer's Enemy," which was written by John Swartzwelder. Despite a life filled with seemingly endless hardships and trials, Grimes earned a college degree in nuclear physics and was featured in a segment of Kent Brockman's newscast. Following that event, Grimes was offered a position at the Springfield Nuclear Power Plant. However, after arriving, Grimes quickly found his opposite in Homer Simpson, the light-hearted buffoon at the center of the series.
Despite Homer's well-meaning but short-sighted attempts to befriend him, Grimes ended up having nothing but animosity for Homer. Soon, after saving the Simpson patriarch's life resulted in a demotion, Grimes declared he and Homer were enemies. Not used to that kind of rejection, Homer tried even harder to impress Grimes, introducing him to his family and sharing his many achievements. However, all of that just enraged Grimes more, as he saw Homer as "everything that's wrong with America."
Grimes soon attempted to humiliate Homer, but the Simpson's co-workers end up celebrating him, thus winning him another easy accidental victory despite his idiocy. In response to this slight, Grimes has a meltdown and mimics Homer's careless attitude. Eventually, Grimes died after grabbing electrical wires with his bare hands.
Grimes has been referenced a few times since "Homer's Enemy," with his grave -- uncared and unmourned -- often spotted in the Springfield Cemetery. Grimes' illegitimate son, Frank Grimes Jr., appeared in The Simpsons Season 14's "The Great Louse Detective," attempting to murder Homer as revenge for the loss of his father. However, he was thwarted by Sideshow Bob, who'd been assigned to protect Homer by the police. Grimes himself -- or at least his ghost -- later appeared in "Treehouse of Horror XXVIII," alongside Sideshow Bob, Kang and the Furious Leprechaun.
Although Grimes' impact on the series in-universe wasn't massive, what happened to him was felt more keenly in the real world. The death of Frank Grimes has been a point of controversy since "Homer's Enemy" first aired. Some interpretations of the episode claim Grimes is right to have so many problems with the lazy and perpetually lucky Homer, while others see Grimes and his fate as a condemnation of people who become bitter at the success of others. Still, most agree Grimes' sudden meltdown and demise is a particularly dark beat.
It also didn't help that "Homer's Enemy" was one of the final episodes of The Simpsons Season 8, which marked the end of the show's Golden Age. While in early episodes of The Simpsons Homer is a blundering, short-tempered and slow-witted oaf, his well-meaning attitude, sweet demeanor and his genuine love for his family and friends make him a likeable character. However, in the seasons that followed "Homer's Enemy," plots began to revolve more around Homer being casually cruel to his loved ones and developing a more selfish view of the world. This new version of the Simpson gets referred to as "Jerkass Homer."
"Jerkass Homer" can be seen as a direct result of Homer's negative traits being amplified in "Homer's Enemy" to make Grimes' point, explaining why some in the fandom really dislike this particular episode. It marks a huge turning point in the series and is thus a portent for a change in The Simpsons' overall tone. While "Homer's Enemy" is a clever exploration of the show's characters and universe, it's also a harrowing tragedy of modern society through Frank Grimes' eyes, and so remains quite controversial.