You've probably wondered at some point while playing: how the heck did Pizzahead build the Pizza Tower? Well, I've got the answer for you, my friend: he's rich.
Looking at the levels, I had a thought: what if he's building a massive farm to grow fresh ingredients?
The most obvious one is Fun Farm, which grows vegetables, but if you look closely, there are other levels that produce things too. Ancient Cheese makes cheese (probably gorgonzola), Refrigerator-Refrigerador-Freezerator probably makes frozen snacks like nuggets and french fries, Crust Cove produces fresh fruit, and Bloodsauce Dungeon produces sauce. And that's just to name a few!
Looking closely, Oregano Desert, Pig City, and John Gutter are the destinations for all this food, the main consumers of Pizza Tower's products. Since these are the levels where you can clearly see people going about their lives, Pizzahead wouldn't just let a bunch of random people live in his tower unless he had something to gain from it, like selling food to them.
Now... Wasteyard and Pizzascare. You know, with all the corpses and stuff. My theory is that these are the dark side of the tower. Levels like WAR, Crust Cove, Fast Food Saloon, and Don't Make a Sound have weapons and things like that. Why would a pizzeria need WEAPONS? My theory is that they're hunting down the tower's residents and selling them as ingredients, while keeping their bones and remains in Wasteyard and Pizzascare.
Now tell me how coherent you think my theory is, and feel free to add anything you want.
Sorry for the bad english