Who created the catch phrase, "I wonder what the poor people are doing today?"

This catch phrase is spoken in south USA many times. Not that I'm trying to get into an argument, but we usually will say this phrase when we are eating a meal beyond our means or budget, because we usually eat from our gardens. Now this phrase may not even fit for this event, but us southerners use a lot of slang. But I have no idea where it originated.

In my part of the country, it's a common expression, or catch phrase (as even defined in the above citation), by no means a slur, and often used by folk of fairly simple means as a humorously self-deprecating comment to imply gratitude for what they have. I'd imagine it to have originated by just such people and taken to the media by an observant author who could appreciate the subtlety.
http://www.thefreedictionary.com/Self-deprecation

Seems like a common "catch phrase" to me. I've heard it a lot.

The saying is part of American lore. It was said often in the South, usually by people who were not so rich.

It was first popularized by Fats Waller, who used to say it after striding up to a piano or at the climax of of a raucous jazz solo. He meant it subversively (he'd often add "I'd like to be doing it with them.")

More recently, Kurt Vonnegut revived it in his "A Man Without a Country" as a cynical but welcome comment made in a basement during the bombing of Dresden.