PJ Robot (also known as Mini-Bot by Romeo) is the tetartagonist of the PJ Masks series. He is a small robot who aids the PJ Masks from Headquarters or in the field. He first appeared in the Season 2 episode "Wacky Floats," but his origins were not revealed until the episode "PJ Robot."

He was originally invented by Romeo as part of a plan to infiltrate HQ. Romeo intentionally made PJ Robot cute and friendly, so that way the heroes would like him and take him to their HQ. However, PJ Robot began to genuinely like the PJ Masks, and eventually betrayed Romeo to join them.