The internet has taught us many things . One important lesson is this : Cats are funny , strange and often unpredictable animals . Their quirky personalities have made cats popular as household pets in homes across the United States . And they are great hunters . Instead , the catch becomes kind of a toy or plaything . Then lets it go . Lets it go . Over and over again ! It is good fun for the cat but frightening for the poor mouse . So , if you play cat and mouse with someone , you play a power game with them . You , the person with the power , are the cat . Maybe you pretend to give the other person something they want but then take it away . You toy with them . We often call a situation like this a cat-and-mouse game . For example , a child might offer something sweet to her little brother and then take it away when he reaches for it . A cat-and-mouse game is filled with lots of action : chases , near captures and repeated escapes . Now , let's leave the game of cat and mouse and talk about playing in a different way . Let's imagine a classroom filled with young children . The teacher must leave the room for a couple of minutes . But the longer the teacher is gone , the more the class acts up . It starts out slowly . Someone throws a piece of paper . A couple of students get up and walk around . Others start laughing loudly . Suddenly , all of the students are doing things they would never do with the teacher in the room . But you know what we say : When the cat's away , the mice will play ! This expression means that people sometimes misbehave when no one is there to watch them . So , the teacher is the cat and the students are the mice . We often use this expression when talking about children and parents , employees and office supervisors and even people in committed relationships .