The city Sideshow Mel asks about during "I'm Talkin' Springfield" is Jacksonville.
Homer's line "Everything I did, I did for you" is a reference to a song from Gypsy, a musical about a vicious stage parent.
Cameron's character could be seen as a parody of the American Idol contestant Clay Aiken.
Also, at one time he is thinking a song of which the beat is the English folk song Greensleeves.
In Lisa's first song, she says she has been to France, however only Bart has been there. The Simpsons went there close to the end of Bart-Mangled Banner. Homer would also go there eventually in a future episode.
Homer once again shows his talents as a musician (he use to be a part of the BeSharps).
Lurleen Lumpkin can be seen standing in the mall audience. Like Lisa, her musical career was also managed by Homer.
Lisa is on the family who did not get food poisoning from the vegetables she ate. In Grade School Confidential, her vegetarianism also saved her from food poisoning. However, she pretended she caught it just because she wanted to leave the party without being rude.
Lisa's relationship with Ralph Wiggum is brought up in this episode where he sang the ABC song incorrectly. After he is finished Lisa say "I can't believe I used to date him."
When we see Carl in the audience from behind, he has yellow skin.
Lisa singing about her cat that she lost at Christmas eve is from the episode, Simpsons Roasting on an Open Fire.