Much like real life. When you meet someone and get to know them they become a certain character in your story. They fit into a mold in your head. When you see them or their name is mentioned a certain feeling comes to mind. It is like they fill a "job" in your life. Maybe they become your comic relief or they are a good listener or fun to go out with. Typecast. The hard part is when they break that mold and start to resemble a new character. We look at them and see the old role. The part they played before. No matter how many auditions they do we just can't fathom that they could fill any new part in our lives.
But what if we opened our minds? We might really like the new character. We might love the new show. We might enjoy their new role in our story.