Colloquial noun for someone who copies others, often used in a teasing or derogatory way.
あの子はいつも私の真似をするまねしだ。
That kid is a copycat who always imitates me.
まねしって言わないでよ。
Don't call me a copycat.
copycat
Formed from 真似, “imitation,” with the agent suffix 師, denoting a person who imitates others.