It doesn't matter a great deal whether you place the pepperoni on the pizza before or after you place the olives and mushrooms in the garbage.
Olives, mushrooms, and peppers all have unacceptable textures, almost as bad as shrimp. Olives should only be used to make olive oil. No fungus should be eaten except the leavening agents in the bread. Peppers should be turned to chili powder or at least dried flakes to spice up the sauce.
No seafood should ever appear on any pizza.
Acceptable pizza toppings include Pepperoni, Italian sausage, Chicken, Pineapple, and Spinach.
Having both Pineapple and Spinach on the same slice would be madness though.
There should only be about half as much of any meat as people usually use on a pizza. I usually take half of the pepperoni off a pepperoni pizza to add it to a cheese pizza, and put a bit if pineapple on both.
P.s. Shouldn't we be talking about the z-axis, not the y-axis?