You can unlock it now by getting the Pizza Penguin plush toy as it comes with a coin for the item. You can also unlock 2 other things from the Treasure Book.
If a penguin has the non-member (not unlockable) version of this item it is considered extremely rare, as the non-member version was only available during the Pizza Parlor Opening Party.
The pizza on the apron has the same design as the Pizza Pin.
The toppings on the pizza does not visible in-game.