Tweaking
Tweaking, also known as Holepunching, is a glitch that first appeared in the fourth generation of Pokémon. It is caused by pressing the left and right buttons continuously whilst holding the up/down button and riding on a bicycle in fourth gear and going through a load line (a load line is from where the game loads the next area graphics). It saturates the DS's RAM making it impossible for the game to load the graphics, and sometimes the values too. It is most easily done in Jubilife City. This glitch will throw up invisible walls or cause a section/route to become black, only seeing the shadows of trainers, items etc. In some cases, the player will be able to walk through a black wall. They may also be allowed to walk through signposts. Tweaking seems to have no negative consequences on the game's data. However, there is a slight chance that while tweaking, the game will freeze. This is solved by simply turning off the game and turning it back on.
In some cases, tweaking may allow players to catch Shaymin and Darkrai. If the player tweaks correctly, then a way to the Mystery Zone can become accessible. If the player navigates correctly, the player might be able to reach the in-game locations of the legendaries mentioned above. Also, if tweaking is done correctly, then a grassy area might appear. In this grassy area, some report finding a bad egg after a three-second pause. Tweaking may be thought as a harder to do surf glitch for other language versions of Pokémon Diamond and Pearl.
