Canned mushrooms. There is no excuse for using canned mushrooms on a simple pepperoni/mushroom/green pepper pizza. If you've run out of fresh mushrooms, take it off the menu until you get more. Green peppers and pepperoni were also half-cooked.
My dinner partners enjoyed their pizzas, however, and I've had OK (but just OK) meals here previously. It's very close to the Rogers Centre, which may explain much about the lack of attention to detail. They should take at least half of the crazy topping combinations off the menu and re-focus on doing the basic ones properly.