The line comes from Fullmetal Alchemist, where Edward Elric, the series' young alchemist protagonist, repeatedly bristles whenever anyone comments on his short stature. His refusal to accept the nickname pipsqueak became a running joke throughout the series, because his explosive response always outweighs the teasing that triggers it. Fans clipped the outburst for anime soundboards and reaction videos, where it spread as shorthand for mock outrage over a small insult. It endures because the joke needs no context: a tiny character furiously defending his height is funny even to viewers who have never watched the show.