Changing Personality Types (CFH)

__TOC__
The above advice is for players who don't yet have a firm handle on role-playing different personalities from their own. And the personalities presented here aren't firm, formal rules which any character has to follow; they're guidelines with no real restrictions placed upon them.
Naturally, then, it's very appropriate for you to write up more Personality Types appropriate to your campaign... if, indeed, you need to formalize them to that extent.
It's also very appropriate for a character to change his Personality Type in the course of a campaign. Here are some ways it can happen:
The Brash Youth wises up and loses his naivete and inexperience. This has to happen eventually (unless he gets killed before he ever gets wise). His experiences in the campaign so far will probably have a strong influence on the next type of personality he chooses. Here's a note for the other personalities: Nothing short of amnesia ever changes a character to the Brash Youth personality.
The Crude Crusher isn't likely to change, but a couple of things could bring about such a change. He could fall in love with a more refined partner, and, feeling gross and coarse in comparison, train himself to become more sophisticated. (The Merry Showoff and Fated Philosopher become good options at this point.) He could have heavy responsibility laid upon him (such as a military officer's commission) and be changed by it (at which point the Natural Leader is a good choice).
The Dangerous Antagonist is only likely to change when whatever made him a Dangerous Antagonist originally is resolved. For instance, if he ever avenges himself on whomever hurt him in the first place, he could change to a Fated Philosopher or Natural Leader.
The Doomed Champion isn't likely ever to change. He's doomed, after all. But if, in the course of the campaign, the DM allows him to un-doom or un-curse himself, he could suffer a change of personality. He could become a Fated Philosopher or Natural Leader. He might enjoy life so much that he becomes a Merry Showoff or Sneaky Thinker. He's not likely to become a Dangerous Antagonist unless the events which freed him from his curse were so nasty that they still scarred his personality forever.
The Fated Philosopher isn't likely to change. This personality type comes at the end of a process of personality development, not in the middle.
The 'Merry Showoff' could sober up under the weight of responsibility, like the Crude Crusher, and become a Natural Leader. Or he could naturally evolve into a Sneaky Thinker when it became less and less fulfilling merely to entertain people and more fun to manipulate them.
The Natural Leader could easily change if dramatic events made him sick and disgusted with always being so responsible and dependable. At that point, any personality except Doomed Champion is appropriate. However, unless he's become totally amoral, even in his new personality he'll probably still have leadership impulses and do a lot of tactical thinking.
The Sneaky Thinker isn't ever likely to change: His way of life is too much fun to him. If he were to change, to become a little less secretive, he'd probably become a Merry Showoff.
For any character, some horrible event (such as the brutal murder of a loved one) could change the character, at least temporarily, to a Dangerous Antagonist or Crude Crusher.