Videogame: Yu-Gi-Oh! Monster Capsule GB

Yu-Gi-Oh! Monster Capsule GB is a Game Boy Color Yu-Gi-Oh! game that was never released outside of Japan. It draws most of its inspiration from the manga's Monster World story arc and the Capsule Monsters stories, using both Duel Monsters and Capsule Monsters.

After Death-T and Seto Kaiba's subsequent coma, the Millennium Ring saw potential in him and corrupted him. Set on revenge, Kaiba extends an invitation to Yugi and his friends to visit his Duel Tower. Once there, the Ring traps Yugi's friends and family inside RPG figurines. The only way to free them is to defeat Kaiba and his minions, the Dark Masters, and enter the RPG worlds and complete the storylines there.

Gameplay is a Turn-Based Strategy game similar to chess. Each monster has different stats and attacking ranges, which can be increased with items. Attacking is calculated by terrain advantages, whether or not an enemy can be attacked by more than one monster, and dice rolls—critical hits and critical fumbles can occur. When monsters are destroyed, they're lost forever, so players must choose battles carefully. In the RPG worlds, random encounters are determined by dice rolls.

This game contains examples of:

  • Bonus Boss: In the postgame, you can duel Joey, Tea, Tristan, Ryou, Grandpa, Pegasus, Bandit Keith, Shadi, Yami Bakura, and a freed Seto Kaiba. The latter two have the toughest monsters in the game.
  • Brainwashed and Crazy: Kaiba's subordinates, as well as Kaiba himself by way of the Millennium Ring.
  • Broken Bridge: A literal example in Rex's tabletop world. You have to find a carpenter to rebuild the bridge to progress.
  • Continuing Is Painful: Losing a battle when in an RPG world results in you getting kicked out of the tabletop game and forced to go through the story again.
    • If you win a battle but lose a monster in the process, that monster is lost forever.
  • Critical Failure: Rolling a 95 or above will make your monster attack itself.
  • Critical Hit: Rolling a 10 or below means a critical hit, with 00 giving you the highest damage possible for one.
  • Demoted to Extra: In probably the only instance of Ryou Bakura getting more screentime than Yami Bakura, the Spirit of the Ring doesn't appear in person at all until after the game is beaten.
  • Easy Level Trick: Seto Kaiba, the hardest fight in the game, can be rendered a Zero-Effort Boss if you bring a Dragon Capture Jar into the fight, which sucks up enemy dragons. Since his team consists of nothing but dragons, you can win without doing anything.
  • Event Flag: These crop up in-story, signified by a chime.
  • Fetch Quest: Most quests in the later RPG worlds involve finding multiple pieces of an item or taking specific items to specific characters.
  • Final Death: Losing a monster means it's gone forever, though this doesn't apply to Yugi's friends.
  • Fire and Brimstone Hell: Seto Kaiba's RPG world is a literal representation of Hell, though only the first layer has fire. The second and third layers deal with lightning and darkness.
  • Guide Dang It: Some walls have easily-missed weak points that indicate you can break them, revealing ways to continue to new areas and progress the story.
  • Killer Game Master: Losing in the RPG World means Game Over, and Kaiba and his followers are determined to defeat you by any means necessary.
  • Magikarp Power: Some monsters are very weak at first, but can become very powerful if you level them up and use an Evolution Chip.
  • Nintendo Hard: Critical hits and fumbles tend to happen at the worst possible times, enemies are often very strong, and despite the encounter rates being percentage-based, you will find yourself in a lot of battles. Also, if you lose a monster it's gone forever.
  • NPC Roadblock: Some NPCs won't move until you either convince them to leave or find ways around them.
  • Prison Episode: Seto Kaiba's RPG World starts with Yugi's imprisonment.
  • Quirky Miniboss Squad: Mokuba, Weevil, Rex, and Mai are Kaiba's four Dark Masters.
  • Random Encounters: These are decided by dice rolls and the number of steps you've taken—for instance, every 10 steps is a 30% chance to be attacked.
  • Save the Princess: Mokuba's RPG World storyline is a typical save-the-princess quest.
  • Spoiler Opening: The intro to the game reveals that the Millennium Ring has possessed Kaiba, something the characters don't learn until just before the final RPG world.
  • Talk to Everyone: A standard tactic to use when in the RPG worlds is to talk to everyone.
  • Toilet Humour: While in Hell's dungeon, Yugi can find a bathroom with urinals but no toilets.
  • The Vamp: Mai flirts with Yugi, to the annoyance of Tea.
  • White Mage: This is Ryou Bakura's character archetype.