Pokémon Diamond and Pearl beta
During the planning and development stages of Pokémon Diamond and Pearl, several parts were going to be a part of the games. Some of them were dropped or changed, but some of those dropped concepts of the beta version can still be found in the game's programming.
Shellos and Gastrodon
A interesting third form of Shellos and Gastrodon has been found. This form is likely a leftover from when Shellos and Gastrodon were planned to be in Ruby and Sapphire. The beta Gastrodon also has various things pointing out from its head in the battle sprite, but is absent from both the male or female sprites. Although this may also be another "unofficial confirmation" of Pokémon Gold and Silver remakes since its PokéDex data states that its colors and shapes differs from region to region.
Other beta-sprites
There has also been discovered other beta-sprites for Munchlax, Weavile and Cherrim. The Munchlax just seems to be a ripoff from the Munchlax-sprite in Dash. The Cherrim beta-sprite was shown in an early Japanese commercial. It is surprisingly like the final sprite, only with the left leg up instead.
Beta maps
A beta-map of Spear Pillar has been found. This is surprisingly like the 'normal' game's Spear Pillar, but it misses the entrance to Mt. Coronet. Many also think that the Mystery Zone found in the Pokémon League is a beta-map.
Beta items
Various items have been discovered by Serebii and various others at Serebii.net and it's forums in the coding of D/P. This items can be got using Action Replay and other cheating-products, but without usage. This also, in turn, reveals others things. These are:
- Boat Ticket, that allows entry for the luxury liner S.S. Anne (this would be a reference to Red and Blue.)
- Contest Pass that would allow entry into Contests. However, Super Contests allows entry without a pass, meaning that normal Contests Hoenn-style would return.
- Magma Rock would be a mystical item that could be used in Stark Mountain. Althrough is han't any known purpose, it is possible it would have someting to do with the Heatran event.
- Red Chain is a creation by the lake trio that would be used to awake Dialga or Palkia. Cyrus actually himself use the item in-game, and it's possible that the Team Galactic event at Spear Pillar not was from the beginning, or, more likely, that it is in the code as a placeholder.
- Rule Book was a book that would be used as a guide when using the Friend Codes or Global Trade Station. It is possible it was meant to somehow got from the academy, Trainer's School.
- Seal Sack holded up to 10 Seals, but was replased with Seal Case.
- Treasure Sack was meant to hold treasures from the Underground. Was replased with with special selections for the Underground.
(Source: Serebii.net)