Well, there goes the neighborhood...a short, short story

I saw him looking out the window, on the fourth story of a brick apartment building that might have been built in the 40's. He was obviously sort of a man-sized bug, but what kind, I couldn't tell from the street, and what with the reflections off the glass window.

A man came out of the apartment building and I looked at him. It seemed as though he was pretty well human, which gave me at least a little hope that the whole place wasn't a big nest or hive of the huge creatures. Altho, as I looked closer at the man, (who had reached the sidewalk, and was now moving towards me) it appeared that his disguise wasn't as good up-close as it was from far away. a small bump stuck out on his forehead, under the skin. In the exact spot where an antenna would be.

"Not so fast Mr. Bug!" I said, and grabbed his neck by the crook of my elbow. "I don't know what you're doing in my neighborhood, or what your plans for humanity are, but I aim to stop you!" Then I began tugging madly at his hair and back of his mask's neck in order to pull it off him.
"Stop!" He cried.
"Never!" I said, pulling like mad at the scruff of his neck, "Not until you tell me what your species is planning to do to the earth!"
"Stop!" He cried again as I got a better grip on the top of his scalp and pulled like crazy. I could feel it move, but it didn't seem as though it would come off."
"Hey! What are you doing!?" Said a passerby.
"This apartment building is full of man-sized insects," I said, "and this is one of them in disguise. I'm going to unmask him and find out what their plans are!"
"Christ, another whacko." The guy said. Then he ran up to try and pry my arm away from the giant insect's neck. Eventually, and with much struggling, they were able to pry me off, however, as they did, I jumped back and whipped out my gun.

"Allright." I said. "Look Mr. I don't know if you're working for them, or if you're just a confused bystander, but whether this bug's dead or alive, I'm going to have his mask off." Then, I addressed the bug in the mask. "So what's it going to be? You've got three seconds before I fire!" The bug didn't move.
"One." I said quickly. The bystander's eyes moved rapidly between me, my gun, and the masked bug.
"Two!" I didn't wait long to say it, and then cocked the hammer back. The bug reached up and began pulling off his realistic-looking human mask. Underneath, wasn't a man-sized bug, but instead a man-sized duck!
"Holy crap!" The bystander said, jumping away from the duck.
"All-right duck." I said, keeping him covered, "What's this all about?"
"Quack." He said.
"So it's going to be like that huh." I turned to the bystander, "Hey buddy, see what I'm talking about!!??"
"Uh, yeah..." He said, confused.
"Well you'd better go fetch some law. Who knows what else is in that apartment building!"
"Yeah," He finished, and took off up the street.

I turned back to the duck.
"So, what insidious plots are you hatching in that apartment building?"
"Quack, quack." He said.
I shot him in the leg.
Lousy ducks.