Brain is the Experiment 837 that is a villainous, magenta-colored version of Stitch with the same abilities, but he is turning into a grayish white, cyborg experiment with a brain on top of his head, a black claws, black stripes all over his body, a small, black spines on his back, and black skin on his chest, his hands, and around his left eye. His alien form resembles a cross between some sort of lizard, koala, and dinosaur with a cyborg appearance. He's sort of Stitch's main antagonist. He has cyborg left arm, two cyborg legs, a iron lower jaw with steel lower teeth similiar to MetalTyrannomon, a half-helmet with a reptilian right eye, a big round ball-shaped nose with a rhino-like horn, and a reptilian tail with cables around it.
- He slightly resembles a Fusion version of MetalTyrannomon from Digimon.