For some reason my kitties thought the word "Hey" implied treat. I guess it's because when I would pull the treats out, usually the kitties would already be in the same room and I would start off "Hey Zelda, would you like some special nom noms?" Which they always replied with sweet meows but, I am guessing this is how "Hey" became the trigger word for treat. Anytime the word was said, I got a meow response--and if I didn't have a treat, it just broke their heart, so they rubbed against my leg and meowed until a treat was given.
Otherwise, the sound of opening cans in general made them think they were eating wet food. Then the sound of opening treat pouches. I couldn't surprise them for nothing!