In the original Borderlands Claptrap was the overenthusiastic robot you probably didn't pay attention to. We all skipped his mission text. Borderlands 2 made our disregard canonical, and Claptrap became the robot nobody liked. He only sounded happy because he was programmed that way, but really he was depressed and lonely. The mission to throw a birthday party for him, which nobody shows up to, was the saddest in the game. But Claptrap wasn't sad – because we were there, it was his best birthday ever. Claptrap went from universally hated to, well, still divisive, but those of us who care about the little guy will ride or die for him forever.
Iconic moment: "Feel free to mingle with, um, nobody."