Johnny Cool does not remember his past, nor his childhood nor his parents. He doesn't remember because he was born yesterday. Built with a patchwork body from various people and given mechanical arms, Johnny was simply born with innate knowledge and personality. His genius creator is presumed missing or dead. But Johnny isn't concerned about the past, but about defining his present and creating his future. Using his gifts, he opened a small and modest private detective agency in order to make a living and to experience life by taking on any job no matter how big or small. But on the side he must contend with a mysterious agency which seems to want to observe and capture him in order to figure out the secrets of his body.
His arms can become hundreds of different gadgets or tools but many of them are unknown to Johnny himself. His arms seem to ignore the Law of Mass Conservation and he can create large and complex mechanisms. He constantly wears his mask because it supplies him with environmental data and a link to his arms and their functions. But he also wears it to hide his face which resembles a patchwork quilt just like his body which has various skin tones. He's tougher and more durable than a normal person, presumably modified in order to support the weight and strain of his mechanical arms. But he can still bleed and be hurt like a normal person. Any damage to his metal arms will self repair over time, using the same sort of technology that powers the transformation of his arms.
Johnny is very preoccupied with his reputation and attempting to establish himself as the World's Coolest Detective. But he strives hard to serve his clients and will go above and beyond for even the smallest tasks. He attempts to maintain a cool and collected attitude at all times but will sometimes get flustered and do his best to hide it. He knows a large amount of encyclopedic information but has zero experiences. Knowledge but not wisdom. For example, if Knowledge is that a tomato is a fruit, and wisdom is not putting the tomato in a fruit salad, Johnny would totally put it in the fruit salad.