A repeating clothing pattern (such as a checkerboard, tartan, or floral print) that doesn't follow the folds and contours of the clothes, body, 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.