PJ was created at Santa's workshop as part of a special experiment to generate good publicity for unpopular animals by distributing cute, fuzzy plushies of them. PJ's brother, Eckert the bat, also came out of this experiment.
In his original comic, Tommy and PJ, PJ was an inanimate toy who was seen as alive only by children and adults with very active imaginations, such as Tommy, Paul, Zuni, L'Ria and Mr. Vier. This changed when the plush toy was merged with an infant robot, the son of Lyn Vocalizer and Magnetta. In an attempt to insure well-rounded development, Tommy's father Xan (the closest engineer Vocalizer could find) hooked the baby robot up to the galactic internet. While logged on, the robot learned all about PJ from L'Ria and adopted the character completely.
Though fully robotic, PJ is covered in grey fur with pink skin on his hands, feet, ears, tail and nose. With eye-shaped lenses over his own eyes, he comes across as completely organic until he opens one of his compartments.
PJ's brain is based on a human brain, allowing compatibility with psionic beings which is not found in normal robots.
PJ's personality is playful, but moderate. Though he acts as the voice of reason to Tommy's impulsiveness, More often than not, he finds himself swept up in Tommy's crazy schemes. He has little patience for belligerence and stupidity, and frequently becomes exasperated with Eckert. His fondness for his brother is apparent, however, especially since he keeps an Eckert plushie in Tommy and PJ.
In the first strip of the "ashcan" version of Tommy & PJ, he claims to be a cybernetic rat playing the part of a plush toy.
PJ's superhero persona is called "Electrick".
His gladiator persona is "Rattus Norwegicus"
PJ's favorite monster is the bugbear.
PJ is able to swim by inflating internal air bladders.
PJ becomes intoxicated in the presence of Magnaradon.
PJ does not like ufek cheese.