Some characters wear a realistic outfit, to the point that a cosplay of them might be relatively simple. But this gets kind of boring; it's not a challenge for the cosplayer to put together, and very few people will actually realize that they are in costume. (Which might explain why even mundane series tend to gravitate towards unique school uniforms and such).
Sometimes the character designers realize that their characters' wardrobes are too realistic. One way to compensate for this is by mixing bits and pieces of what might be a number of perfectly acceptable outfits into a bizarre Frankensteinian mess. The outfit may be comfortable, but something about it just looks slightly, but not totally, off.
Often involves Too Many Belts, Goggles Do Nothing, Virtual Paper Doll (with some questionable mixing and matching), Impossibly Tacky Clothes, Fashionable Asymmetry.
An especially bad example may have you asking, "What The Hell, Costuming Department?".
This is typically justified in settings where characters are forced to scavenge and fabricate clothing or armor from whatever scraps they have at hand. It's especially prominent in Post Apocalyptic fiction.
