Correct, but na-apers have more of a meaning of someone who repeats what is said. See: http://en.wiktionary.org/wiki/parrot
While a copycat often is someone who steals someones work and call it their own.
http://en.wiktionary.org/wiki/copycat
In danish, I think the word is hard to translate into anything else than "efteraber" or "efterligner". Or maybe, with good will, you could say "papegøje", which is a parrot.
would "kan nogen venligst sige at der ikke kun er efterabere" be correct?