Pokémon FireRed and LeafGreen beta

, as remakes of, implemented redone elements of the original games. Nonetheless, as individual games, they have gone through similar stages of development as all the other core series games.

Pre-release
Early sprites for and  were seen in a pre-release screenshot published by Dengeki Online.

A different sprite for Professor Oak that would have been used in the New Game tutorial of the games was seen in a Japanese commercial. This commercial also shows the color-based text distinction for male and female NPCs that the localizations would adopt, which was not used in the Japanese versions (instead, they use two fonts to make the distinction).

Sevii Isles
More routes were planned for the Sevii Islands. However, each one of these routes that are still programmed in on is called Sevii Isle (Japanese: ななしま Nanashima), suggesting that they are islands instead of routes. Their Japanese name is shared with that of the Sevii Islands, with the only difference being that the Sevii Isles use as opposed to the Sevii Islands' usage of.

Counting from the "first" route in the Sevii Islands, Kindle Road, and going down numbers the Sevii Island routes into the same order reflected by the Sevii Isles, suggesting that the routes of the Sevii Islands were originally intended to be numbered in this way.

The location name data programmed in for the Sevii Isles is:
 * Sevii Isle 6 (Japanese: ６ばん ななしま Nanashima 6)
 * Sevii Isle 7 (Japanese: ７ばん ななしま Nanashima 7)
 * Sevii Isle 8 (Japanese: ８ばん ななしま Nanashima 8)
 * Sevii Isle 9 (Japanese: ９ばん ななしま Nanashima 9)
 * Sevii Isle 22 (Japanese: ２２ばん ななしま Nanashima 22)
 * Sevii Isle 23 (Japanese: ２３ばん ななしま Nanashima 23)
 * Sevii Isle 24 (Japanese: ２４ばん ななしま Nanashima 24)

Sevii Isles 6 and 7 have map data consisting of only a single tile. Sevii Isle 6 has a tile that can be surfed on, while Sevii Isle 7 has only a tile that cannot be walked or surfed on. Sevii Isles 8 and 9 have fully programmed map data, implying that they were scrapped very late during development. The music theme that plays on all four is ナナシマ Sevii Islands if the undefined enters them by land.

If the Town Map is opened at Sevii Isles 6, 7, 8, or 9, it displays the player's location as if they were near. Additionally, their index numbers are located after Three Isle Port and before Resort Gorgeous. This may mean that they were originally routes on Four Island.

No wild Pokémon are programmed into these areas by default. No index pointers lead to them by default either; on Sevii Isle 8, the central island on the route has what one would assume to have been cave entrances changed into the side of a rock.

Sevii Isles 22, 23, and 24 have their location name data placed between the Tanoby Ruins and Navel Rock. If a map is given the header of Sevii Isle 22, 23, or 24, the player's location will display as if they were near the Tanoby Ruins. Additionally, the unused maps with pointers $0033560C, $00336170, and $00337814 in the English version ($0033560C, $00336170, and $00337814 in the Japanese version) are stored immediately after the Tanoby Ruins as well, which may mean that those maps were originally intended for use as Sevii Isles 22, 23, and 24.

Other locations
The following maps are also unused:
 * a house interior found in the data of, , and with no events or warps
 * duplicates of Celadon Hotel and restaurant
 * the copy for the main room without boxes blocking access to the second room and the second room itself of the Mystery house in  (the e-Reader cards for use with  in Japanese versions are for the Trainer Tower)
 * the copy for the main room without boxes blocking access to the second room and the second room itself of the Mystery house in  (the e-Reader cards for use with  in Japanese versions are for the Trainer Tower)

The maps below appear to be related to other maps.

Items
Key Items exclusive to (and also ) are found within the internal data, complete with item sprites and Bag descriptions that differ from those of Ruby and Sapphire, due to their different layout and menu setup, which allows less space for the descriptions. These items are only obtainable by cheating or modification of the saved game data. For the most part, they have no use, though the and  will act the same as the normal Bicycle obtainable in FireRed and LeafGreen with the exception of not being recognized by the games for entering.

HM08, unobtainable except by cheating and containing like in Ruby, Sapphire, and Emerald, can be taught and deleted freely, making its use almost the same as a normal TM.

Music
Audio track with index number 0x0119 in the ROM plays an unused version of Pokémon Healed which is a chiptune-like rearrangement of the regular theme used by the games, and that also resembles the original theme from. This may hint at a planned earlier implementation of a feature like GB Sounds.

Sprites
Unused overworld sprites of, , , , , and 's Attack and Defense Formes have also been discovered in the internal data. Their use is not known but it is possible that they might have been planned for s. Many of the trainer class sprites were carried over from Pokémon Ruby and Sapphire but go unused as well. While no TMs in Generation III were of the, a TM disc sprite does exist for the Bug-type.

Weather
The overworld weather effects are carried over from but only a few are used. Like its predecessors, don't use the "four snowflakes falling" effect.