Roach

You and your team used to make jokes about the new guy Roach. Because of his call sign, because you thought it was short for "cockroach." At first Roach was neutral to the joke until it got that far.
You particularly enjoyed making jokes at him because he didn't respond in any way, but you knew you were pissing him off. Maybe you liked him, but you didn't want to admit it. On one of those same ordinary days, you were alone with him. You started to make jokes in his direction, but he pinned you against the wall with a sharp movement, first looking at you and then "flicking" your nose.
"Leave those jokes alone," he said calmly, letting you go, and parallel moving away from you. - "Because I'm not a cockroach."