6. Store-bought Halloween Costume - There’s no rule that you have to go out on Halloween. That being said, there is one that you’ll look like a giant dweeb if you buy a prepackaged costume at the store. No matter which costume you choose, when you buy your costume at the store, the only thing people will see you as is an uncreative, cheap material-wearing fool. On top of all that, not making your own costume pretty much guarantees that someone else at the party will be wearing the same thing—which can be pretty humiliating, especially when that other person is twelve-years-old.