>>12118884
when mario runs up the side of a wall, a different set of sprites was used, which are shown in the rightmost column. without the ratio correction, his body appears stretched out like in the top row.
the proportions of his body match more closely in the ratio-corrected sprites, suggesting that it was designed with a 4:3 image in mind, meaning the pixels are supposed to be slightly rectangular rather than perfect squares as they appear in emulators.