Homer goes through the evolution from prehistory to modern history from unicellular to human. When Homer finally gets to the couch, Marge asks him "Did you bring the milk?" and Homer sighs in exhaustion.
The episode starts with the Simpsons family escaping Church. Homer is in such a hurry that when Lisa falls over he decides to leave her but Marge declines and goes back to get Lisa. Marge decides she wants to eat out instead of cooking for herself as usual. After finding out every place has lines, Marge goes as far as to break into someone's apparent party. It does not take long for them to realize that they crashed a funeral. Homer volunteers to be a pallbearer, filling in for a man who has twisted his ankle. After falling into an open grave, Homer is sent to the hospital.
While at the hospital, Homer finds out his usual "D'oh!" did not sound as right as usual. While causing the bed to sit upright, and lay flat, Dr. Hibbert notices Homer's diaphragm is safely under his stomach when he is lying down, giving him the ability to sing in an operatic voice that causes newborn babies to cease crying and weak patients to feel strong.
While shopping for organs, Mr. Burns overhears Homer and immediately hires him to sing the lead in his production of La bohème. Homer wows the crowd at the Springfield Opera House. Homer becomes an enormous celebrity who consistently receives attention from older aged women. While running from a mob of his crazed fans, Homer is saved by a person on a motorcycle he assumes is a man, however at the home "he" is revealed to be a "she", named Julia. When Marge goes into the kitchen to bring tea, Julia strips naked and says she wants to have sex with him, and threatens Homer that she will tell Marge Homer attacked her if he tells. Over the next few days, she keeps appearing in sexually suggestive positions. Homer, soon enraged, fires her.
Next morning, Homer finds a poisonous cobra in his cereal box and then, after grabbing it, repeatedly whacks it on the refrigerator causing it to be dazed for the remainder of the morning. Lisa worries someone is trying to kill Homer. At Homer's next performance, Chief Wiggum goes to general measures, none of which are useful. Julia arrives to shoot Homer with a poisonous blowdart. While Marge saves Homer, the shot fires through a French Horn and back into Julia's neck. Every sniper in the opera house starts shooting at Julia, although all but one miss. She is taken to the hospital, vowing revenge on Marge. Homer gives up opera to work on his new passion: painting.
The episode had 8.43 million views tuned in. Robert Canning of IGN gave the episode a poor review (4.5/10). He found the plot contrived and found Homer's rendition "If Ever I Would Leave You" unfunny. He did enjoy the episode's opening scenes in the church. Richard Keller of TV squad said, "I thought the episode itself was okay with a few good laughs". He went on to say, "Not only does Castellaneta have a very good professional voice, but he seemed to adapt to all of the Italian opera verses that he needed to sing during the episode."