Guinea pigs are very cute pets, and have also often been used in laboratory tests and experiments. Someone may also be called a “guinea pig” if they are a test subject for something new. “We have a new English examination, and this year’s students will be the guinea pigs.” The expression can be used when someone is trying a new experience. “I’ve got a new recipe I’d like to try making before I serve it for a party. Will you come over for dinner and be my guinea pig?”
Elephants are rather large creatures that would stand out if they were ever in someone’s living room. If you hear the idiom “elephant in the room,” the speaker is referring to a controversial topic that everyone can see but no one wants to talk about. It is a useful expression when people at an event avoid discussing an obvious issue because it’s uncomfortable to speak about. “We enjoyed John’s birthday, but the elephant in the room was that we all knew he and his wife are getting a divorce.”
In the United States, people used to buy cans of worms to use as bait when they went fishing. When the cans were opened the worms would try to wriggle away. From this comes the expression “to open up a can of worms.” You try to solve a problem, but instead you discover other hidden problems. “An audit of the company finances opened up a can of worms and now the chief executive is under investigation.” People often use this phrase in the negative if they are afraid of causing extra trouble and inconvenience. “I’m not going to complain about my boss’s behavior because I don’t want to open up a can of worms.”
It’s difficult to shuck an oyster — that means to open an oyster shell — but your reward might be a beautiful pearl. That gives us the phrase “The world is my oyster.” It comes from Shakespeare’s play The Merry Wives of Windsor. When someone says this, they mean that they have many opportunities to make a profit or gain an advantage. People often say this phrase to young people to emphasize that they have many choices that can lead them to wealth or happiness. “I don’t know what to do with my life.” “You have just finished university and you’re still young — the world is your oyster!”
Another seafood-related expression is the phrasal verb “to clam up.” When a clam encounters a predator it may close its shells together to protect itself. If someone is refusing to talk or to give up information, they are often described as “clamming up.” “The thief clammed up during the police interrogation and didn’t say a word.” Like a clam protecting itself from a confrontation, the phrase suggests that someone doesn’t want to look at other people in the eye and instead looks down at the ground. “My son always clams up when he is guilty of something.”