Friendship underflow

This glitch only works in Pokémon Diamond and Pearl

It allows you to quickly raise the Friendship of any Pokémon. Consequently, you can rapidly evolve Pokémon such as Buneary that require a Friendship value greater than or equal to 220 to evolve.

Usually, items like Energy Powder and Energy Root decrease the Friendship value by 5 and 10 respectively (10 and 15 if Friendship is between 200 and 255). If you decrease the Friendship value by more than 2 below 0 during a fight, the value will become negative. But the value being coded as a 16 bit unsigned integer, it will simply overflow to a great positive value.

As stated above, this is quite useful if you want to evolve Buneary quickly, because its base Friendship value is 0 :

• Buy 1 Energy Powder in Eterna City • Catch a Buneary in Eterna Forest • Lose some HP and use the Energy Powder in a battle • Run away

The Friendship value of Buneary is now 251, just level it up once and it will evolve into Lopunny. You can also teach it Return at level 13 to hit pretty hard, since Return's base Power is equal to Friendship divived by 2.5.

If the Pokémon you want to evolve isn't Buneary, refer to the base Friendship of the Pokémon you want to evolve, and use as many items as needed to make the value negative. Example : Riolu has a base Friendship value of 70, meaning that you will need to use 8 Energy Root during the fight.

Base 0 : Buneary Base 70 : Golbat, Eevee, Pichu, Igglybuff, Togepi, Azurill, Budew, Chingling, Munchlax and Riolu Base 140 : Chansey and Cleffa