Wiley burned the oatmeal. The black in the bottom of the pan looks like it's about a half-inch thick. This will require an all-day soak. I put some salt in the pan, and if that doesn't work, I'll try the baking soda. A few other sites suggested boiling vinegar (but that would smell just as bad as the oatmeal), boiling dishwashing soap, or using Coke to clean it out. Coke is now a delicacy, so I shan't be trying that.
Burned oatmeal smells awful. Yuck.