I know a stupid INTJ. The general effect seems to be that he's INCREDIBLY paranoid, rather aggressive and tends to only want people around him when he needs them for something, when he wants them to just do what he wants and then go away. He's always convinced he's right and thinks he's a lot smarter than he really is, so he tries to trick people and lie to them, not realising that everyone's onto him in seconds because he just really has no idea of how dumb he is and how transparent, consequently, his lies are. He's also absurdly competitive and insists on winning everything, including a two-player game of Mario Kart with a six year old, every time, and lecturing her on the importance of winning and trying to step up to the mark when she starts crying.
He's really not a very nice person to know... I don't know how much of it's due to INTJ-ness or dumbness, or what, but he's a real pain.
I think though, that the stupid NT would be likely to attempt to do all the same things that a smart one does, only he'd fail with it most of the time due to overestimation of his ability, underestimation of others' abilities and then probably blame everyone/everything else for it.