The only thing that can effect a big change in personality is something that physically rewires the brain and/or alters the body's chemical milieu.

In the room where I work, I have a chalkboard, and as I'm going along, I write the made-up words on it. A few feet from that chalkboard is a copy of the full 20-volume Oxford English Dictionary, to which I refer frequently as a source of ideas and word roots.

Like every other creature on the face of the earth, Godfrey was, by birthright, a stupendous badass, albeit in the somewhat narrow technical sense that he could trace his ancestry back up a long line of slightly less highly evolved stupendous badasses to that first self-replicating gizmo---which, given the number and variety of its descendants, might justifiably be described as the most stupendous badass of all time. Everyone and everything that wasn't a stupendous badass was dead.

But I'm not a small-literary-novel kind of guy, and once I'd developed the world in the first couple of hundred pages, I felt that there was potential here to go on and write an engaging story set in that world. So that's what I did. This probably ruins things both for the people who want small literary novels and for those who want action-packed epics, but anyway, it's what I wrote.

Wait a minute, Juanita. Make up your mind. This Snow Crash thing—is it a virus, a drug, or a religion?" Juanita shrugs. "What's the difference?

The franchise and the virus work on the same principle, what thrives in one place will thrive in another. You just have to find a sufficiently virulent business plan, condense it into a three-ring binder ― its DNA ― Xerox it, and embed it in the fertile line of a well-traveled highway, preferably one with a left turn lane. Then the growth will expand until it runs up against its property lines.

Just as an informal, nonscientific observation, most people's personalities don't seem to change very much during their lives. There are exceptions in the case of people who go through hugely traumatic events or suffer from brain injury or disease. Some would argue that religious conversions can have deep personality-altering effects. But these are all exceptions to the rule.