1, similarity in appearance: Doo and Sue have similar appearance features, such as face, eyes, nose and mouth. It makes people feel like they look alike.

2. Visual errors: There are some visual errors. Because of the similarity of hair style, clothes and other external characteristics, people mistakenly think that Doo and Sue look alike.

3. Psychological influence: There are some psychological influences. For example, in daily life, people tend to regard people who are similar in some aspects as similar, even if they are not exactly the same.