copycat
/ˈkɒpɪkæt/noun
1- informal, derogatory (especially in children's use) a person who copies another's behaviour, dress, or ideas〈非正式, 贬〉（尤指孩子用语）盲目模仿他人行为（服饰, 思想）的人; 仿效者。
1.1
- as modifier denoting an action, typically a crime, carried out in imitation of another模仿他人的行为（一般指罪行）：
copycat killings
模仿他人的谋杀。