Werewolf, princess, ninja -- these are the kinds of generic costumes you buy in the "costume" section of the grocery store, because you're either a stupid kid who doesn't know better, you're an adult who's not all that into Halloween, or you're just broke as shit and too lazy to make something interesting, so you're hoping that you can slip a Frankenstein or two onto the food stamp card.
If you're a kid, this costume choice is totally fine: Literally any night that you get to wear unorthodox clothes outdoors is basically going to be the best time of your life, so you go on with your bad self. You proudly holler at everybody that "you're a vampire" like it's gonna blow their little minds, get as much candy as your wispy frame can bear and try not to get your weird little kid germs on my doorknob.
Just leave the bowl outside; they're like little petri dishes with adorable speech disorders.
If you're an adult, but you're just answering the door for the trick-or-treaters, this is also an acceptable course of action. Because seriously, who gives a shit? The kids see you as a malfunctioning vending machine, spitting out candy bars into the empty night. They are not going to care what you're dressed as, or if you're dressed up at all -- they only care if you're handing out Smarties, and brother: God help you if you're handing out Smarties.