This might get old after a few minutes' wearing, but it's certainly amusing at first glance:
I think my sons would love it. A green shirt with an "earth" type tie-dye design, light brown dye for the "crust" and red and yellow "chaos" in the middle. The toppings - pepperoni, bell pepper, mushrooms, and olives - must be printed on, from the looks of it. Screen printing is best and most durable, but an opaque iron-on print, if you cut out each piece separately, or hand-painting with opaque fabric paints, would work, too.