My characters, as well as being formed by evolution and years of toil, are products of their environments. Their environments strengthen and weaken various parts of their personalities, and let other portions break free.
Again, we’re going to use Geoff as an example.
Geoffrey grew most as a character once I started messing around with his location. After being brought from medieval to Victorian England, Geoffrey became more…likeable. His personality and quirks began to develop around this time period; he acquired a profession (inn keeper) and other characters began to weave their way into his life. Thanks to the other characters and the environment that they provided, Geoff (and they) grew in different ways.
In respect to the current WIP, I can already see how an early location change will affect my MC’s personality. Originally, he was going to end up in Holland following an accident. Now, after a little bit more research, Jim’s staying in England (and above the English channel). His relationships with his fellow pilots (not to mention the others around him) will push him into a different direction than his adventures in Holland. Perhaps we’ll meet his family, which in itself will bring out a side he’d rather not expose, I’m sure.