People around the world love their pets . And in the United States , cats are very popular . But they are not just popular as pets . Their often strange and funny behavior has made them really popular on the Internet too . So , it is not surprising that American English has many cat expressions . In past programs , we have talked about several of them . But today we focus on one expression that features another animal – birds . Birds such as sparrows , finches , robins and canaries are fair targets for these skilled hunters . Today's program centers on the canary . With its beautiful feathers and lovely bird-song , many people keep canaries as pets , too . So , if a cat eats one , it may have a look on its face that shows both pride and guilt . The cat is happy it did it even if it is wrong to eat a fellow pet . Now , do cats feel guilt and pride ? But people do . You can also say “swallowed ” instead of “ate .” This look is not one of honest pride for hard work or a great achievement . If looks could talk , this one would say , “I just got away with something and you have no idea what it is . I should not have done it and I know it was wrong . But I am still pleased with myself !” The expression “to look like the cat that ate the canary ” says all of that . When using this expression , don't forget the guilt part . Let's say you have a friend who studied really hard on a test and then scored really well . She feels proud of her accomplishment . Her smiling face shows it . But you would not say to her , “Well , don't you look like the cat who ate the canary . The expression does not work that way . However , if she did not study but still passed because she cheated and still looks proud about it … then the expression will work quite well . Now , we use this expression in other situations . Maybe we know something that no one else does and it shows on our face . We have a secret . We may look like the cat that swallowed the canary . We use it when we are really pleased with ourselves – when we feel smug . What does “smug ” mean , you might ask . When you are smug , you are TOO proud of yourself – to the point where other people are upset or annoyed with you . People who look like the cat that ate the canary are also hiding something from others or simply not telling all the details . One word for that is being coy . Find a chance to practice with today's expression – “you look like the cat that ate the canary .”