B-4
Data, Lore and B-4: the good, the bad and the retarded. B-4 is another android constructed by Doctor Noonien Soong. He appeared in the abomination Star Trek: Nemesis and is just as stupid as the film is.
The Enterprise-E find B-4 in pieces on a pre-warp planet and taken him back to the ship to be assembled. They decide to transfer Data's memroy to B-4, blissfully forgetful of the disasters they faced dealing with Lore.
B-4 reveals himself to be part of the clone's master plan and tries to break into the Enterprise's computers. He is caught, and Data takes his place in order to get onboard the Scimitar and rescue Picard.
At the end of the film, following Data's destruction aboard the exploding Scimitar,there are hints that Data's programming still flows in B-4's circuitry, and that -- like Spock -- Data may return from oblivion.