A copycat is what you call someone who copies everything you do.
When someone copies everything that you do they are called a copycat.
Copycat is a term that is used in either a slightly derogatory way or lighthearted way.
When someone copies everything that you do, it often means they are either trying to fit in with you, admire you, or lack a strong sense of self and are using you as a model for their own behavior.
The copycat behavior can be interpreted as a form of flattery, but if done excessively, it can also be seen as annoying or a sign of insecurity on their part.
Copying others is a natural subconscious behavior in which people subtly mimic other peoples actions to build rapport and connection and can be considered normal in small doses.
Someone might also copy another person if they are unsure of their own identity and see them as someone that they want to emulate.
Copying behavior can also be a way of trying to gain another persons approval or fit in with a group.
If someone is also envious of others styles or success, they might copy them to try and appear similar to them.
Another word for copycat is impersonator or strong matches.