Repeating patterns (such as checkerboards, tartans, or floral prints) that don't follow the folds and contours of clothes, hair, etc. at all. If there's no repeating pattern, use double exposure.
Featured in many, many anime, as it's much cheaper and easier than adjusting the pattern realistically. Particularly noticeable in stylized or minimalistic shows such as Sayonara Zetsubou Sensei and Bakemonogatari.
