Don't mess with the Fish. From Wikipedia:
"McDonald's removed the Filet-O-Fish from its menus in the United States on September 26, 1996,and replaced it with the Fish Filet Deluxe sandwich, which was part of McDonald's ill-fated Deluxe line of sandwiches. However, the Filet-O-Fish was brought back to its menus on a gradual basis starting in the middle of 1997, due to overwhelming letters and petitions, receiving the larger fish patty from the Fish Filet Deluxe. The Fish Filet Deluxe itself was discontinued at most restaurants early in 1998, while others still offered it until 2000, when it was finally removed from all McDonald's menus."