Just a quick update: the ABC Mart is now the A Mart. Same store, same owner, same staff. Just a different sign and still right between the 7-11 and the Candy Cane Inn. So don't anyone be confused if you don't see the same name. Between the 4 stores at the Katella and Harbor intersection, there's a very good chance you'll find what you're looking for. If you want more than just snacks, there is a Target about a mile south of the parks on Harbor. And people use
Amazon Prime/Pantry/Fresh/etc. and Vons.com for grocery deliveries to their hotels.