mimic

A mimic is someone who copies or imitates someone else's actions, words, or behavior.

You might see a mimic at work when an actor does a great impression of their favorite celebrity. They try to sound like them and even move around just like they do on screen. A mimic can also be someone who follows fashion trends closely, copying the way others dress and style themselves. Mimics often use what they've learned or observed from others to create something new and original.