The Oak's Parcel prevented progress glitch is a glitch in Pokémon Red, Green, and Pokémon Blue (Japanese), as well as both the Japanese and English versions of Pokémon Yellow.
This glitch prevents the player from being able to deliver Oak's Parcel and obtain the Pokédex, because Professor Oak rates a non-existing Pokédex instead of accepting his parcel. As the old man in Viridian City stops the player from being able to go north towards Viridian Forest if the Pokédex wasn't obtained, it is impossible to progress, though making 'progress' with glitch techniques from an expanded items pack is possible.
In Red, Green and Japanese Blue, it is a natural glitch. In Pokémon Yellow, the send party Pokémon to a new game glitch or 255 Pokémon glitch is required, because the walking Pikachu cannot evolve, and the player cannot trade until delivering Oak's Parcel and obtaining the Pokédex.
Evolution method (Red, Green and Blue only)
- Start a new game, and progress until defeating or losing to Blue.
- Level up the starter Pokémon to level 16 or above, and evolve it.
- Professor Oak won't accept his parcel when you return to his lab. He will rate a non-existing Pokédex.
Send party Pokémon to a new game method
See send party Pokémon to a new game for more information.
The player can send over at least one Pokémon that can be evolve, preferably Caterpie as it evolves as early as level 7 and has the medium fast experience type, and then evolve it.
When the Pokémon are transferred over, the Pokédex data is not, meaning that obtaining Pikachu counts as having one Pokémon, but when Caterpie evolves into Metapod, the number of owned Pokémon will change to two.
After the number of Pokémon changes to two, Professor Oak won't accept his parcel.
255 party Pokémon glitch method
Due to the 255 party Pokémon glitch enabling corruption of the number of owned Pokémon, it's possible to pull off the prevented progress glitch with it, but the simplest method does not fully demonstrate the glitch, as the player seemingly can't finish the initial battle with Blue and then go and obtain Oak's Parcel from the Viridian City Poké Mart.
Through a more complicated method involving a wrong warp and depositing many Pokémon, it's possible to obtain Oak's Parcel and then finish the battle with Blue.
In Pokémon Yellow, with the 255 party Pokémon glitch, it's possible to change the number of Pokémon owned in the Pokédex to over 1 by swapping the first Pokémon with the seventh, eighth or tenth.
This lets Professor Oak rate a non-existing Pokédex before you even battle Blue. If the player were to finish the battle with Blue and obtain Oak's Parcel, Professor Oak would not accept it, but there is apparently no way to see this, as progressing after the battle with Blue with the 84 Pokémon (originally the player has 255 Pokémon, but when they obtain Pikachu it changes to 84) is seemingly impossible.
Full demonstration of the glitch
More research is needed for this article.
Reason given: Investigate freezes when trying to deposit Pokémon, test these steps in languages other than English and French Yellow.
A full demonstration of the glitch via the 255 party Pokémon glitch is possible with the following steps:
- Swap the first Pokémon with the tenth to get 255 items.
- Select the 36th item and toss 255 of it. Its quantity represents the memory address D364 (exit destination). If the player stand on the right-most tile on the exit mat, it will be a Master Ball x0.
- Exit your house to warp to Viridian City.
- Go south to Route 1, and use a Master Ball in the expanded items pack at position 30 to capture a Magmar and set the number of Pokémon to 51. If a Master Ball isn't in position 30, try another Poké Ball.
- Obtain a Potion from the Poké Mart worker on Route 1 to set the number of items to 0.
- Head back to Viridian City, enter the Poké Mart, and receive Oak's Parcel.
- Deposit Pokémon in the PC until the number of Pokémon is below 6.
- Return on the way to Pallet Town to have Professor Oak take you to his lab.
- Obtain Pikachu, and preferably save at this point as the next part requires luck.
- Go battle Blue and have Pikachu not faint. Professor Oak won't accept the parcel.
Note: One may have to clear the items pack only after depositing the 51 Pokémon in the French version to avoid freezes caused by trying to select or deposit the party Pokémon.