To my cat, all food is tuna fish until proven otherwise.

My cat Ahab doesn't like people food, except for tuna fish. And he doesn't even like the fish itself, he just likes the water from the can. I've had the habit for my entire life of giving a little water from the can of tuna to the resident cat(s) so they'll stop meowing at me while I make a sandwich. Once I've spoiled the tuna with mayo they're no longer interested, and as long as I don't give them more than a flake or two of actual tuna there's no barfing or unhappiness.

Anyway, Ahab is finicky to the point that he won't eat cat treats, so until a couple of years ago he didn't bother me about Tuna and I didn't give him any tuna water. But then I did, and he liked it, so now he's decided that anything that requires standing at the counter to prepare must be Tuna. He meows when I'm cutting up an apple; he meows when hubby makes a cup of coffee, he meowed at me this morning when I was putting shedd's spread on a bagel.

Generally putting the food in question under his nose makes him shut up and go away in a huff, once he realizes that it's not tuna, but hubby gets alarmed when I do that because he's afraid Ahab will stick his nose in my food, and he's more fastidious than I am (hubby, I mean. So is Ahab, probably). Every other cat I've had or known can tell the difference between tuna and not-tuna from approximately one block away, but Ahab just has to see for himself, I guess.