Skyla was originally conceived as a Dragon-type gym leader, while Iris was conceived as a Flying-type one. These attributes were swapped relatively early into development: examining character pitches for both gym leaders found in the Teraleak (a large-scale breach of internal server data from Game Freak in 2024), the earliest recovered revisions are the only ones which describe them with their initial type specializations. From the second revision of the documents onward, they bear the same types seen in the final game.

Of note is that Iris' later pitches describe her Dragon-type specialization as stemming from a connection that she felt since birth. Given that these subsequent drafts change her ethnicity from "indigenous" (likely Mesoamerican given her use of "Aztec-style" hair decorations) to "Middle Eastern," these traits imply that she is intended to be multiethnic (as within Middle Eastern cultures, dragons are found in Canaanite, Mesopotamian, and Persian mythology, while her outfit, a galabeya, is generally associated with rural Egyptians).

Among the files included in the Teraleak, a massive breach of internal server data from Game Freak in 2024, are early overworld sprites for various prominent NPCs in Pokémon Black and White. These sprites feature various differences compared to the final game:

• Grimsley is blonde instead of dark-haired, coincidentally resembling Barry from the Generation IV titles.
• Elesa doesn't wear stockings and features a more curved set of headphones.
• Brycen's palette is overall darker, he wears a face mask instead of a domino mask, and his robe shows much more skin compared to the final game.
• Skyla has much darker skin and brown hair tied in pigtails resembling a bird's wings. This design, which was radically overhauled in the final game, is likely a more literal interpretation of later revisions of her character pitch (also included in the Teraleak), which describe her as a dark-skinned Hispanic character inspired by Latina celebrities such as Jennifer Lopez (who is ethnically Puerto Rican) and Isabeli Fontana (who hails from Brazil, which is a Latin American country, but not a Hispanic one on account of its Lusophone population).

In-battle sprites for several characters are also present in the Teraleak's assets. Notably, while Elesa's in-battle sprite reflects her early overworld design, Skyla's in-battle sprite is light-skinned and blue-haired, indicating that Game Freak were considering alternate design options before ultimately settling with her final look, which features red hair, a significantly different hairstyle, and a complexion that matches the "slightly dark-toned" description given in the earliest version of her pitch (which more specifically describes her as South American, matching Fontana but not Lopez).

Within leaked source code for Pokémon Black and White uncovered by the Teraleak (a large-scale breach of internal server data from Game Freak in 2024) is an unreleased Nintendo DS remake of Yoshi, which according to the commit notes was intended to test multiboot functions for the two games. Various traits in the remake suggest that it was ported from a prior attempt at a Super Nintendo Entertainment System version instead of being made with the DS in mind: its name on the title screen is Super Yoshi no Tamago, while its copyright notice is listed as 1995 and credits Ape Inc., which had shut down in the same year. Furthermore, gameplay takes place exclusively on the bottom screen, and there are no touch control features present.

The remake only has one stage, an underwater level. Mario uses Jill's voice lines from Drill Dozer while Yoshi retains his modern voice. The game is also riddled with bugs, featuring corrupted title screen graphics, a nonfunctional mode selection screen, and a glitch where the game may lock up if certain button combinations are pressed. Due to the Teraleak only containing fragments of the Pokémon Black & White source code, it is unknown if these bugs reflect the state that Super Yoshi no Tamago was in when it was abandoned.

When Pokémon Black 2 and Pokémon White 2 first released in Japan, fake leaks were posted on various websites claiming to be ROMs of the game, but in reality contained an FMV of a parody of the theme song to the Disney Channel series Cory in the House. The parody featured several of the games' characters and other memes at the time superimposed over the actors' heads, including talk show host Stephen Colbert, a caricature of the Pokémon fan website Serebii.net with a Trollface superimposed over it, and legacy Pokémon character Gary Oak. Before the title card of the show appears at the end, a barely visible screenshot of a post from the imageboard 4chan can be seen featuring the box art of the Nintendo DS game adaptation of the show, implying that the parody and fake ROMs originated from there. The video also features several scrolling text statements including:

• "Amber killed Gary" - supposedly referring to an incident on 4chan's dedicated Pokémon board /vp/ starting on August 26, 2010 where several posters using Gary Oak and Mewtwo as avatars tried to "revive" or "kill" the anime-only character Amber from The Uncut Story of Mewtwo's Origin by trying to predict their post numbers in advance.
• "SHE IS BLACK ?!?" - referring to Pokémon Black & White Gym Leader Lenora.
• "GIANT HAIR EVERYWHERE" - on the following shot with four Bouffalants superimposed over Mount Rushmore.
• "FINAL GYM LEADER (IT HAS BEEN SEREBII CONFIRMED)" - referring to Iris, the last Gym Leader in Pokémon White and seems to be referring to leaks from the first Pokémon Black and Pokémon White games.
• "THIS FLOATING TEXT IS UP IN YO' SCREEN DAWG"
• "AMERICA" - on a shot of Stephen Colbert.

An upload of the fake ROM's FMV on YouTube dates back to September 16, 2010, two days before Pokemon Black & White's release date in Japan, and features several comments mentioning 4chan and /vp/ on top of the references in the video, suggesting that the hoax actually dates back to the release of the first Pokémon Black and Pokémon White, although discussion of this FMV from that time does not appear to have been preserved. While this ROM is also not known to be preserved (though its contents are), as recently as 2018 there have been reports of ROM dumps of Pokémon White 2 being silently modified to include Cory in the House references, including NPCs with dialogue featuring the lyrics to the show's theme song.

In Generation V, the sounds that play with each individual hit of the move Thrash sound extremely similar to the opening notes of the "Ground Theme" from Super Mario Bros.

The Pokemon Audino's design was created for the Pokemon Anime first and foremost. Artist Ken Sugimori stated he wanted a Pokémon that would look good alongside the series' Nurse Joy just like Chansey did, as he knew the Anime would go the same route as Black and White, and would feature an entirely new roster of Pokemon.

According to an interview with Ken Sugimori, Deino and it's evolutions, Zweilous and Hydreigon, were originally desinged to be cyborg tanks, but the idea was scrapped, then revived to look more like the mythical Yamata no Orochi.

Sugimori stated in the interview, "Deino, Zweilous, Hydreigon. At first, these incorporated an army tank motif, and the marks that look like a conveyor belt on the upper part of Zweilous's legs are the remnants of that. Initially, they didn't work as designs and were basically 'put to sleep', however, a three-stage powerful Dragon-type family was ordered and they were resurrected."

The game contains unused hidden abilities for certain Pokemon. They include a Zapdos with Lighting Rod, the Snivy family with the ability Contrary, and a Chandelure with Shadow Tag.

In the beta version, when buying items at a Pokémon Center, the part of the screen where the player can be seen is rotated.

Darumaka is designed after a Daruma doll, both having similar markings and neither being able to be laid out on their sides.

Game Freak has its own building in Castelia City. They appear on floor 22, the same floor as in their real life office in Carrot Tower, Tokyo, Japan.

According to game scenario author Toshinobu Matsumiya, Hilbert and Hilda were initially visualized to be 16 years old.

During certain occasions, the spirit of a deceased young girl will be standing on the bridge, and will disappear if the player walks towards her. An old lady in the gate to the east of the bridge will explain that the young girl used to play around the area with an Abra before the bridge was built. In the sequels, the girl will also appear in Strange House where she will refer to Abra and the bridge before telling the player to return the Lunar Wing there, which will trigger a battle with Cresselia.

The idea of having two rivals instead of one came from early concepts for the Pokemon series that went unused until Black & White.

Fans believe a number of areas in the game include music that sounds similar to music in Mother 3, such as Pokemon's "N's Farewell" and Mother 3's "Love Theme," and Pokemon's "Surf Theme" sounding like Mother 3's "The Green Train's Fun Too!"

None of the songs in the game are confirmed to be inspired by the Mother series.

There are unused 3D models for both Dialga and Palkia from the title screen of Diamond & Pearl. There are also logos for Pokemon Diamond and Pearl in the data, probably because Black and White were built on top of those games.

Genesect's backstory is similar to Mewtwo's. Both were created by villainous teams in at least one canon (Team Rocket for Metwto and Team Plasma Genesect), and genetically engineered and enhanced to be more powerful.

Prime numbers had a significant role in the composition of N's battle theme. Though there is little evidence to suggest this in-game, N is actually a mathematical genius. It can also be said that he sees the world in a 'black and white' fashion, using formulas to make sense of it.
Composer and director Junichi Masuda frequently references this in N's battle theme with the use of prime numbers, and even more so with the addition of sounds like a clock ticking in N's final battle theme.

The GTS has a filter to prevent Pokémon with inappropriate nicknames from being traded. However this prevented Pokémon, such as Cofagrigus, from being traded without nicknaming it because their name contains a keyword. This has been mostly fixed but some Pokémon, such as Nosepass, are still unable to be traded without a nickname.

On Route 10 in the original Pokémon Red and Pokémon Blue, Picnicker Carol gives a description of a chunky, pink Pokemon with a floral pattern. This description is what Munna was based on.