In New Super Mario Bros., each power-up has a specific index that picks the effects of the power-up from a list. While there are only few different power-ups, the list itself accepts entry numbers up to 256, the vast majority of which result in unintended effects.
Most power-ups that use unintended entries are some variety of what is shown in the footage: an effect that discolors Mario and causes him to grow uncontrollably, similar to the beginning of the Mega Mushroom animation. However, instead of stopping when Mario is a specific size, he will simply keep growing indefinitely until the game crashes.
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