copycat

Short definition from Wiktionary

Noun

1. 1
   One who imitates or plagiarizes others' work.
2. 2
   A criminal who imitates the crimes of another; specifically, a criminal who commits the same crime, especially a highly-publicized one, that has just or recently been committed by someone else.

Adjective

1. 1
   Imitative; unoriginal.

Verb

1. 1
   To act as a copycat; to copy in a shameless or derivative way.