The phrase “can of worms” (sometimes written as “can-o-worms,” depending on the context) can refer to a number of things. There is an idiom involving a “can of worms”, where the “can of worms,” or rather the worms within the can, are being understood as a piece of information or conversation topic that will cause problems. Hence, one often hears statements like “don’t open that can of worms,” meaning one should not bring up a certain subject – the contents of the “can of worms” – because of the problems it may bring about.