interplanetary ninja assasin. its an easter egg [ <-- wrong it isn't an 'easter egg' it is a reference to some other thing most likely from a tv show or somthing but what it means in the actual expansion is that the robot was re-programmed to take out the vault hunters as that (in the storyline of the game) would be the, hence 'ninja assassin'as nijas and smart and cunning and if you watch the movie at the start of the expansion it tell you he didn't attack them directly merely piss everyone else off at them and 'interplanetary'is a reference to the hyperion- the company that reprogrammed it and owns all of the claptraps any way and they also own many planets like the other coporations in the game such as Atlas in Knoxx's Secret Armoury and Jakobs in Dr. Neds(totally not Zed) Zombie Island expansions ]
The Interplanetary Ninja Assassin Claptrap (INAC) is actually a hint in game. It wants to show that there is something more to do. The INAC is a direct referance to the DLC4, where this claptrap is the leader of the new robot revolution.