I was listening to an OTR show “Burns and Allen” and Gracie asks her houseguest what kind of cereal he’d like
Gracie) Would you like cereal
Guest) Fine
Gracie) We have puffed, flakes, whole, shredded and cracked. I personally prefer cracked.
Of course the idea is that Gracie is half crazy so she would like “cracked” cereal. <insert laugh>
But what is that?
Well, Jimmy cracks corn and I don’t care. Or, I’m researching this from a corn angle because the song is stuck in my head.
One Google result for “crack corn” claims that cracked corn is for farm animals, so maybe Gracie is saying she likes the animal feed form of the grain. <insert laugh>
Another result, which has a song origin against the Straight Dope column on Jimmy Crack Corn, says it was punishment food for slaves.
Cracked wheat, though, is basically bulgur, which I usually see in savory dishes, not sweet. Cracked oats seem (from Google results) to just be another type of grain to use for oatmeal.