▋Imitater's namesake is a portmanteau of the words "imitator" and "tater", a slang for potato.
▋The Imitater may be a representation of a mime, as it is black and white and wears a beret.
► A beret is a soft, visorless cap with a close-fitting headband and a wide, round top often with a tab at its center. This type of headgear is mostly used in Military Service.
▋For some strange reason, the Imitater plush toy has no "legs".
▋The Imitater acts like the Pokémon Ditto: he transforms into other plants while Ditto will transform into another Pokémon.
▋Imitater is the plant equivalent for Presto, a character in Insaniquarium, a game also made by PopCap. Just like the Imitater, Presto can turn into any kind of pet.
source:
http://plantsvszombies.wikia.com/wiki/Imitater没有特定的人