Cerberus’s behavior is a clincher for Percy: monsters aren’t all that monstrous if one treats them like what they are on the inside. Though Cerberus may look monstrous, he’s really just a neglected dog who longs for playtime and a friend—his goal isn’t to hurt or kill people. The effect this has on Annabeth shows that she, like Percy, understands that Cerberus isn’t all that bad. She also recognizes that she’s made another friend that, by many metrics, she shouldn’t have. This continues to help Annabeth see that she can be friends with anyone, if only she makes the effort to do so.