Threefold PP Up removal glitch

The threefold PP Up removal glitch is a glitch derivative in Pokémon Red, Blue, and Yellow with a negative effect.

If a PP underflow glitch is used when the player has two or three PP Ups applied and one PP remaining on the move, the trick will give the player 63 PP but remove one of the PP Up effects. The trick can be performed up to three times to remove all of the player's PP Ups.

Explanation

The threefold PP Up removal glitch works because the amount of PP left and the number of PP Ups used are stored in the same byte, with values of +0x40, +0x80 and +0xC0 meaning 1, 2 and 3 PP Ups used respectively.

When the underflow occurs, it is possible for the PP to no longer have a value of +0x40, +0x80 or +0xC0. For example: if the player has a value of 0x41 in the PP byte, it means they have 1 PP left with 1 PP used. An underflow may cause the PP value to drop by two and become 0x3F, which means 63 PP with no PP Ups applied.