I was heading into Wegman's (an awesome grocery store in Buffalo and Erie) to get some bread and carrots when I thought about wielding a katana. I had taken kendo classes in college and I tried to remember the correct stance and technique for the various strikes. I thought about taking more kendo classes in the future and imagined showing up to class, telling sensei that I had taken kendo before, and then promptly assuming an incorrect stance. I further imagined that I would be vindicated by further practice as the lessons that had once sat rusty in the back of my brain received a good polish and demonstrated to sensei that I had taken classes before (I simply neglected any practice since then).
And that spurred the thought for the new character. I imagined someone who knew the basics of any job/skill but always appeared very out of practice. It would be obvious to anyone acquainted with that job that he was not a complete neophyte (there would be hints that he knew certain advanced details of a job) but he was not at the top of his game. With a little practice, however, he soon resumed his full competence.
This being the City of Dimension, such a man would need a weird origin for his ability. I decided he would be a corporate being, the collective consciousnesses of multiple people throughout space (and maybe time) given corporeal form. He possessed the knowledge and skills of all these people but it took some time and effort to bring about full access and familiarity (he would, in essence, need to strengthen the established bond to a particular consciousness until the skill operated as his own). He would be a drifter or a homeless man, wandering the streets of Dimension and finding work wherever he could. By choice or by fate, he is drawn to temporary jobs; in those cases where he is offered a full-time position, he inevitably abandons the post after a short time. It is not in his nature to be tied down or adopt a routine existence.
He needed a name. The name that kept popping into my mind was Jack. It was not a deliberate play on jack-of-all-trades but it may well have been a subconscious motivation. For a last name, I somehow came to Dufresne (do'-frayn). He is gritty, hard-worn, probably smokes, often has a mean case of stubble (rarely a beard), and somehow keeps his light brown or blonde hair cut short. He has brown eyes (or blue or green, if blonde).
Obviously there needs to be a yet greater secret about Jack Dufresne. A corporate entity like himself must exist for a reason, whether to accomplish something (like, for an example off the top of my head, the consciousnesses which compose him come from victims of some immortal supernatural creature and he has to solve the mystery of their deaths and remove the dopplegangers that exist in their place) or as a result of something else being accomplished (like, for another example off the top of my head, a supernatural EMP ripping parts of the souls from people and them coalescing into this new being who must find his own purpose in life but might also want to investigate that EMP).