When Charlie's parents decide that he is responsible enough to have a pet, he gets a mouse named Nibbles. Both he and Lola soon begin having a lot of good times with Nibbles. They teach him many tricks and he proves to be the cleverest pet on "Bring Your Pet to School Day." When Nibbles passes away, Lola seems more broken up about it than Charlie. Charlie helps Lola to see that he's sad too, to cope with the loss and to ultimately celebrate what they both love about Nibbles.