The Stop bug is a bug found in the Super Nintendo version of Final Fantasy IV. The Stop spell causes various strange behaviors when cast on enemies affected by other timer-based status effects.

When Stop is used on a target that has a timer-based status such as Sap, as soon as the timer restarts, many strange issues will occur. For instance, if Stop was applied to a character that is under the Sap status, the character will lose HP indefinitely until a Sap inflicting attack such as Bio resets the timer. A number of other status timers behave similarly, to potentially keeping a permanent Paralyze to characters or causing the game to freeze when used on enemies. The Sleep and Paralyze status with Stop for enemies were fixed for the North American version of Final Fantasy IV revision 1.1 and Final Fantasy IV Easy Type. The game won't freeze in those versions.

Here is a list of timer-based statuses that are affected by this bug:

• Paralyze: This will cause the game to freeze for enemies or characters will stay paralyzed indefinitely in the Super Nintendo version.
• Sleep: This will cause the game to freeze for enemies or characters will stay sleeping indefinitely in the Super Nintendo version.
• Gradual Petrify: This will cause the game to freeze for enemies or characters will stay partially petrified in the Super Nintendo version.
• Sap: In the Super Nintendo version, the timer stops for enemies and characters. However, the characters keep losing their HP indefinitely until KO or when the battle ends. The Gameboy Advance version doesn't prevent the Sap timer to stop.
• Regen: The timer doesn't end in the Super Nintendo version which allows the effect to last indefinitely.

The Dispel spell also messes with Stop's timer in all Super Nintendo versions, this bug was fixed for the Gameboy Advance version. One of the lesser known things is that Dispel can remove Stop's timer on a character with the Doom status. However, it doesn't properly check for the Doom status, so when the player casts Dispel on a character under the Stop status, they are under permanent Stop status until Stop is cast on the character to reset the timer. It doesn't affect enemies the same way.