Green with one eyes
They first appear in Cat Got Your Brain? (Series 2 Episode 18) so they could study Shaun and Pidsley. One of them spills the coffee on the control panel, and the other one pushes buttons frantically, so no changes can be made. Unfortunately, this causes the machine to malfunction, switching their brains, then the spaceship tilting left and right, moving back and forth, dropping Shaun with Pidsley's brain in the Farmer's house, then dropping Pidsley with Shaun's brain in the barn.