When you're on the Planet of Hats for too long, someone's hat is going to fall off. The probability of this happening seems to be directly proportional to the flamboyance of the hat. That is, if Bob's planet is filled to the brim with Blood Knights, who proclaim "The greatest glory is to die in battle!" and "Only the strong survive!" over dinner, expect Bob to be a Pacifist.
There are a number of reasons why this happens:
There is a Writer on Board who wants to do An Aesop about hypocrisy or just an excuse to show why the Proud Warrior Race Guy has defected to a rival group.
So that the human characters can show their inherent moral superiority by demonstrating that they really care more about honor than the Proud Warrior Race Guy.
Deconstruction: Real people don't come from the Planet of Hats, and when you've got an entire species who has only one character trait among them, there are only so many interesting stories you can tell before you've got to make the characters more complex.
Plain old logic: Think about which individuals among them would choose to go live and work with humans.
Often happens to races who seem at first to be Always Chaotic Evil, resulting in them proving themselves to be Not Always Evil thanks to the occasional Token Heroic Orc. May lead to an Enemy Civil War as those who reject the hat fight the ones who love it. Despite the fact that the Klingon Scientists Get No Respect, they may not believe this trope and choose to "rebel" in order to enable their peers to wear their hat.
This trope's name comes from the oft-(mis-)quoted line from William Shakespeare's Hamlet, "The lady doth protest too much, methinks." Note that in Shakespeare's time, "protest" meant "proclaim solemnly or firmly" (which, in context "the lady" was suspiciously overdoing). That's the opposite of its modern western connotation, "dissent loudly", although it still occurs in "Protestant Christianity" and "to protest one's innocence".note Using the example from above, Bob's warrior species "protests too much" by overly avowing violence, when all Bob wants to do is flirt with Alice the Granola Girl. It could also work with the modern definition, in that they are protesting against Bob's behavior.
Related to Cultural Rebel, Disappointing Heritage Reveal, Stop Being Stereotypical, and Stereotype Flip. All of the Other Reindeer is a variant of this. Square Race, Round Class is when the character's job (not necessarily their personality) contrasts with expectations of their species. Rogue Drone is an instance of this within a Hive Mind. Compare Father, I Don't Want to Fight and Pro-Human Transhuman. See also Black Sheep and White Sheep. If Bob is seen as more admirable by outsiders for having rejected his hat, You Are a Credit to Your Race may be invoked. When every member of a race that we see subverts their supposed attribute, it becomes an Informed Attribute.
