Copycat

A copycat, a person who may not realize or does realize that they are copying you but will never admit it. It may come off as mirroring, but once it starts showing more and more that they’re basically emulating all the actions and phrases and way you express yourself, you’ll notice that they are TA DA! A copycat.

He’s such a copycat, he always does things or says things similarly to how I do them. It’s annoying!