Pokémon Underground

AdvanceMap is a program for Windows used for modifying map data in GBA Pokémon ROM hacks, first released on April 15, 2003. The program would remain the standard for use in the ROM hacking scene until it was succeeded by Porymap in October 2018.

Hoax image purporting to be a leaked regional form of Oddish in Pokémon Scarlet and Violet. The image was first posted to 4chan in April 2022.

Am amusing addition to yesterday's post about Pokey, the "Pikachu Virus". Wikipedia's page on the worm was required to blur the image of Pikachu due to a copyright notice. Notably, Wikipedia pages about official Pokémon content have received no such notices and use unblurred official artwork.

Top: Pokey, more commonly known as "The Pikachu Virus", is a Windows email worm first reported in June 2000. A user would receive an email like the one seen above, with a "pikachupokemon.exe" file as an attachment. When run, this executable would send a copy of this email to every address in the user's address book, then add a line to the PC's startup routine to format the system.

Bottom: However, an oversight in the code means that the user is first prompted as to whether or not they want to delete the directory and all files in it. Simply typing "N" in response to this prompt will allow the user to boot their machine with no damage.

Unlicensed skateboarding Pikachu toy.

Top: Regular battle theme from Shi Kong Xing Shou (commonly translated as Space-Time Star Beasts), an unlicensed Taiwanese monster collecting RPG, released for the Game Boy Color in 2001 by Vast Fame. While the game features many assets modified from other titles, including Pokémon, it features an original story, world, characters, soundtrack, and gameplay, and has garnered a cult following. It uses the sound engine from Mega Man V.

Bottom: Arrangement of the theme from Star Beasts Comet Version, a ROM Hack of Pokémon Blue Version loosely based on Shi Kong Xing Shou. Alongside monsters from the original game, the game features redesigned and brand new creatures, plus an original world and story of its own. It uses the sound engine from Pokémon Crystal Version.

Cover of Issue 32 of Beckett Pokémon Collector Magazine, an unofficial magazine that covered the franchise. The magazine ran for 127 issues from September 1999 to July 2010.

An unlicensed Rayquaza toy. This photo gained significant memetic attention online in 2024, but it was being shared online as early as April 2016.

The packaging for the Action Replay DS and Action Replay DSI cheating devices feature "knockoff" artwork of characters from many Nintendo DS games, prominently including Pokémon. The devices were not officially licensed and thus could not include official artwork or character designs.

Top: Characters seen on the packaging for Action Replay DS.

Bottom: Characters seen on the packaging for Action Replay DSI.

In early 2026, one of the printers used to print a run of Pokémon Trading Card Game Basic Energy cards wasn’t properly cleaned before being used for printing Magic: The Gathering Lorwyn Eclipsed Commander decks. This resulted in at least one run of the decks having a faint layer of ink showing the blacks from Basic Energy cards.

Screenshots of Shoddy Battle, an online battle simulator released in July 2007. The site simulated Generation IV gameplay, and was affiliated with the competitive battling website Smogon University until 2012, when the popular Pokémon Showdown! simulator was first released into beta.

Visuals associated with the Buried Alive Model creepypasta, which alleged the titular character existed unused in the code for Pokémon Red and Blue, and was intended to be a boss in Pokémon Tower before being replaced with the Marowak ghost. The sprites were created by the artist QueenKami in September 2010.

Unlicensed Shaymin plush sold by online distributor Top Dream.

Home page of the Geocities site Jacob's Pokémon Paradise.

The Pikachu Nightmare is a ROM Hack of The Smurfs' Nightmare occasionally seen on unlicensed multicarts. The Pikachu Nightmare is seemingly unrelated to Monster Go! Go! Go!!, another more common Pikachu-themed hack of the same game: They share no assets or code that didn't originate from the base Smurfs game. Whether one was inspired by the other or this was merely a case of convergent design is unknown.

Monster Go! Go! Go!! is a colorized ROM hack of The Smurfs 3 featuring Pikachu, previously covered on this blog due to its humorous opening cutscene featuring Meowth singing an unusual rendition of "My Heart Will Go On" from Titanic. Significantly rarer is the game's direct sequel Monster Go! Go! Go!! II, a similar hack of Kirby's Dream Land 2 released by the same publisher.

Opening cutscene of Monster Go! Go! Go!!, featuring Meowth reciting a bizarre version of "My Heart Will Go On" from the film Titanic.

The game is a colorized ROM hack of The Smurfs 3 for the Game Boy, and it appears commonly both on multicarts and standalone unlicensed cartridges. Likely due to unoptimization in the process of adding full color to the game, it also runs much slower.

The Smurfs 3 would later be officially colorized and rereleased as The Smurfs' Nightmare, and in turn this hack was remade based on that version of the game and released as Pokémon Action Chapter.