Bugs:Super Mario World (NES)
This page details bugs of Super Mario World (NES).
Due to a programming error, the game requires you have 101 coins to get a 1-Up, rather than the standard 100. This isn't too big of an issue, however, since your current coin amount carries over between levels.
On a similar note, collecting five Dragon Coins in a level is supposed to give you a 1-Up, but the aforementioned error means the game checks if you have more than five Dragon Coins rather than at least five. Since Dragon Coins do not carry over between levels, there are never more than five in any given level, and they don't give any points on their own, the Dragon Coins are rendered entirely pointless.