As other posts have stated, how does the allegory of racism work this series has never established the racial or ethical background of characters with the exception of a Christmas special (more on in a bit)? It was not set up like what the graphic novel,
Maus, did for the Holocaust.
The aforementioned Christmas special, which came out in 2000, was the only time it revealed these traits. And it was only two of the main cast with Francine being Jewish and Brain's family is of African descent, I guess, since they were celebrating Kwanzaa.