Dealing with children often, and now a pregnant wife, I can say that eating well is often a luxury. You have to get the time to cook, and find the small portion of foods that they will actually eat. And Kid Cuisine isn't as bad as half the crap we all eat. Working as a chef I can attest that the same chemicals found in frozen dinners are found in more items than you think.

As for the item itself. If it is poo, there is no doubt that a disgruntled worker put it there. And since most of the major assembly lines don't have people in contact with the food. It's seems just as likely that something stuck in the oven, burned, then stuck to the bottom of the next pizza.