A.J. created this robot to act as a "big brother" to him, and to protect him from menacing school bullies such as Francis. The robot was able to dispatch Francis quite easily with a laser beam, but was destroyed after self-destructing when it saw how awesome Timmy's older brother was.
The AJ-5000 is a silver colored robot with a single red eye that can shoot a non-lethal laser beam. The robot moves around on a single wheel. Apparently, this robot can feel emotions. It became so depressed that Timmy wouldn't be its brother that it said "I am nothing." and self destructed.
This robot appeared in "Oh, Brother!" as one of several characters introduced that were protecting their "younger brother" characters. The robot only defended A.J. and not the other students, so it was useless to Timmy Turner when Francis turned his attention to him instead. A.J. carries a small remote with a button that, when pressed, causes the robot to zap whoever is threatening A.J. with a laser from its red eye.
The AJ-5000 was destroyed when Timmy wished up his own older brother. The robot saw how much cooler Tommy was, and self destructed in shame when Tommy said that he was only there for Timmy. The robot's head landed near a playground set that Tommy, Timmy, and Tootie were playing in.