YELLMONS

https://tcrf.net/Proto:Pok%C3%A9mon_Yellow

This is a debug build of Pokémon Yellow. It is based off the final English release, so no Japanese skills are required to play. To most, this appears to be a regular copy of Pokémon Yellow. However, if you press select (space) on the title screen, it brings the player to a debug menu. The 2 options you get are FIGHT and DEBUG. The fight menu allows you to make your own team of Pokémon by selecting their index number between 1 and 190 as well as their levels, between 1 and 100, you also can choose the Pokémon that the opponent has. Also the player name is "Tom", which I find interesting as there is no one named Tom mentioned anywhere in the credits. Perhaps one of the debuggers was named Tom, and there were other copies with the names of other testers, who knows.

On the other hand, the DEBUG option is much more interesting. The player starts with every badge in the game except for the final badge. This may have been for playtesting purposes, or to discourage reviewers or people from magazines from spoiling end game content. The player also starts with 4 Pokémon. A level 80 Snorlax with a full set of HM moves, a level 80 Persian, a level 15 Jigglypuff and a level 5 Pikachu. Interestingly, the Pikachu starts with the move Surf, which allows the player to play the lesser known Pikachu's Beach minigame on Route 19, which was originally only accessible to players who got it from Pokémon Stadium. In addition, the player can disable wild encounters and even trainers from spotting them simply by holding B (w on this emulator). The Pokédex is also 100% completed with all 151 Pokémon as both seen and caught. The player also has numerous items in their inventory to assist with playing and exploring the game, including 99 master balls, 99 escape ropes, 99 rare candies, 99 fresh waters (presumably for giving to one of the guards around Saffron City), the S.S. Ticket, the Secret Key (to unlock the 7th gym) as well as the bicycle. They also will start with the maximum amount of money possible.

Hilariously, although this is well known, the player in debug mode starts with the name Ninten. Seems ordinary, it's just a reference to Nintendo. But the rival name? SONY. Of course, this was around the same time span when the Nintendo 64 was competing against Sony's Playstation.

Regardless of whether the player starts in debug mode or not, interestingly, inside of the player's bedroom, on the right side, there are also warps to numerous Team Rocket based encounters, possibly for testing warping to numerous areas, although why those specifically, I don't know. Perhaps since Team Rocket had a part in the Pokémon cartoon/anime (I haven't watched either though), it made it easier for the playtesters to get screenshots of the encounters, even as late as Silph Co.