Apu was really the first Hindu on television, to my knowledge. I remember Time magazine running an article on the significance of that character. And yes, you're right, they've done a good job of fleshing out his character over the years (graduate of Calcutta Inst. of Technology . . .)

Carl, Dr. Hibbert, and Judge Snyder are all educated blacks with good jobs, but they're all kind of bumbling. Carl, along with Lenny, is one of Homer's sidekicks at work, and most of the humor associated with him is slapstick. Dr. Hibbert laughs at inappropriate things and is just a good-natured chucklehead. Judge Snyder used to be a serious character but now they've turned him into the liberal judge who lets everyone off easy - a perception of many black judges, I believe. I never thought about this stuff before now.

You may recall Smithers being black in the first few episodes. When they sent the cells to be painted in Korea or wherever, they just randomly painted characters, which created a problem, since he was supposed to be a "white sycophant." Didn't become gay until later . . .

"...let my children hear music - for God's sake - they have had enough noise."
Charles Mingus