"It's funny. Every crook I meet wants to tell me how much I'm just like them."We're not so different, you and I. In another time, another place, I might have called you friend! Two characters who seem radically different turn out to have more in common than they would like to believe. As a good thing, the frequent resolution of an Enemy Mine or Locked in a Freezer plot: two enemies learn that there is more that unites them than divides them. The punch line to about 50% of plots in an Odd Couple or Odd Friendship series. As a bad thing, the realization that our hero isn't as far from villainy as he thinks. The hero may realize how close he is to crossing the line, and spares the villain. Or he'll decide that it's worth crossing the line, off the villain anyway, and then have several episodes of moral anguish over the darkness in his soul. Or he might never notice the similarity at all. If the audience notices this but the characters in the story do not, it could be a sign that the trope is being used by accident, which usually results in a Designated Hero or Designated Villain situation, among other Unexpected Reactions. And, at the other end of the scale, it's entirely possible — and easier than one might think — to cite or invoke the trope on purpose but poorly, creating a false equivalence. For example, a character who kills to save his loved ones or after being left no choice is not necessarily Not So Different from a character who kills purely For the Evulz. The same morally questionable (or admirable) action can be taken by different characters for different reasons; motivation and context are important in distinguishing whether a similarity between characters is meaningful or superficial. Sometimes goes hand-in-hand with a Double Aesop, You Could Have Used Your Powers for Good / Evil, We Can Rule Together, or He Who Fights Monsters. Can also be phrased, "You would have made a good thief / assassin / Klingon / Mandalorian / Dalek / Minbari / Troper / Wikipedian." Compare Your Approval Fills Me with Shame, where the villain outright compliments the hero on his Dirty Business. Contrast Commonality Connection. Compare and contrast Sympathy for the Devil and Sympathy for the Hero. Sometimes, the difference is only that the heroes are A Lighter Shade of Grey. Hitler Ate Sugar is when this trope becomes a logical fallacy based on the idea that sharing any similarity with someone 'evil', no matter how minor, makes the sharer just as evil. This trope also happens to be a staple of many a Break Them by Talking. Can also come with much Foe Yay.
— Edward Elric to Psiren, Fullmetal Alchemist