Just a sketch. I decided to play around with the original idea that Rattrap was handi-capable (thumbs up!). His lower body was blown off while working as a spy on Cybertron and was replaced by four wheels that now fold nicely under his rat-mode hips. Due to his accident, he was forced to retire from his spy work and became the chief mechanic for Vespa Mining Co. He then decided to re-join the military and enlisted as a mechanic for the maximal star fleet. He got stuck working on some creaky old bucket of bolts called the Axalon on an uneventful assignment under some pilot named Optimus Minor (who was later easily compelled to change his name due to a strange new set of circumstances). Little did he know... And y'all can fill in the rest. His trademarked "exposed brain" look doesn't make sense if you consider that these are alien robots. Why a human brain? The insides of those armor panels on his arm are magnetic, and are used to house tools he'd use as a spy. His wheels are jointed in several ways to allow him total mastery of his movement and the wheel itself is made of a sort of "smart-rubber," which adapts to whatever terrain he's on at a thought.