copycat
n.n. someone who copies the actions of another person, often in a way that is annoying or dangerous. It can also describe a person who tries to be like someone famous or powerful.
n. a person who imitates the actions or appearance of another, often in a manner perceived as inferior or unoriginal. In a legal or social context, it refers to an individual who replicates the behavior of a previous perpetrator, typically in a criminal or violent act.
He is a total copycat who always wears the same clothes as his friends.
The police are investigating a copycat who seems to be following the same pattern as the original thief.
The rise of social media has made it easier for a copycat to mimic the public persona of a celebrity, often leading to a dilution of the original brand's identity.
Originally American English, from copy + cat (“former derogatory term for a person”).