Say you need a character who is going to do something unexpected, like turn their friend in to the enemy, or suddenly stick up for that guy who's about to be pulverized by the big baddie. Would you rather have a character who has secretly been for the other side all along, or one who changes their mind at a critical moment? Would it make a difference if the character was your main protagonist or antagonist, versus a side character?
Both ways can get the OMG factor. Both can have the reader re-examining the character's past actions for clues. But one represents a change in the character, and another a change in the circumstances. One is the character saying "I was wrong to build this popsicle stand in the middle of the diabetic unit" and the other is the character saying "time to blow this popsicle stand. With bombs."
Feel free to answer/ramble in the comments. If the question inspires a Flash Friday or something similar, feel free to link to your story in the comments and please link back to here on the applicable webpage.
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