Yeah Apu started as just a stereotypical side character but he's evolved from that. Unlike other characters that just show up once in awhile for a one note joke (like Bumblebee Man), Apu has changed into a full fledged character.

Remember that episode where Apu becomes an American citizen? So much good stuff in there that subverts the immigrant stereotypes that these people who want to ban Apu are fighting against and really challenges the notions of what makes a person an American.

The person most ignorant about American history and government is Homer, the guy who's claiming loudest that he's protecting America from the threat of immigrants. It also touches on politicians misdirecting voters to the "immigrant threat" to distract them from other issues, Apu's motivations for wanting to be a citizen, and Moe's internal shame for being an immigrant. So much good stuff there and done in a way that's funny as hell and still manages to be heartwarming.

"First they came for Apu, and I did not speak out— Because I was not Indian.

Then they came for Bumble Bee Man, and I did not speak out— Because I was not a Mexican.

Then they came for Dr. Hibbert, and I did not speak out— Because I was not black.

Then they came for me—and there was no one left to speak for me."