Rex has developed a personality around the concept of a caretaker. It has assumed the needs of its owner to be its prime directive, even such tasks that have not been requested of it. This results in Rex often flitting about in an attempt to meet any possible task before it is necessary, including menial tasks.

Rex makes a mark that is immediately apparent upon first setting eyes upon it. Looking like the victim of an explosion of color, Rex is covered in multi-hued designs and patterns utilizing as many variations as possible. While appearing to be random upon first glance, there is a certain uniformity to the chaotic display of the artist.

Rex has received specialized programming and upgrades around the operation of its motivators and actuators, that allow for much smoother and subtle movements than a standard KX-series Security Droid. This additional programming slightly reduces the reflex time and movement speeds of the droid.

Rex has had its programs re-written and mechanical systems hard-wired for combat operations. This augmentation gives this KX-series Security Droid a significant increase in combat efficiency in eliminating targets on behalf of Jasper Arlow, but at the expense of it being usable for much else except for combat.