He looks like a brain with eyes and a mouth just like the rest of Brain Pods . He is pink.
At some unknown point in his life he started working for Evil Emperor Zurg . In this capacity he came up with several inventions for the Emperor. During this time he lived on Planet Z like the rest of the Brain Pods . However, something made him choose to leave Zurg's employ and he defected. Zurg hires infamous bounty hunter Shiv Katall to kill the Brain pod. However, instead of trying to kill the brain pod, Shiv Katall, who is really Buzz Lightyear in disguise, arranges to meet up with the Brain pod in a secret underground bunker located in Zurg space and take him to Star Command where he will be given a new identity.
After Mira , Booster and XR cause problems with this plan, XR comes up with a new idea to get Brain pod 13 out of Zurg Space and to freedom. He has Brain Pod 13 disguise as Brain Pod 18 , by simply using a pen to change the number "13" into "18." The rangers then hide and have the brain pod simply transfer them all off base. However, this plan meets with failure, when Emperor Zurg runs into the real Brain Pod 18 and realizes his mistake.
Commander Nebula also assuming the Shiv Katall persona also tries to mount a rescue. Again the plan is to sneak out right from under Zurg, with Shiv supposedly transporting them to Planet Z when in reality they would escape to Star Command.
Presumably increased intelligence since he is a brain and a scientist.