Almost all boss Pokémon found at the end a 99 floor dungeon have a 99.9 percent base rate of being recruited, meaning the player won't have to slog through the hour-long level again just because they got unlucky.
Anyone you recruited before or will recruit will be playable.
And Now for Someone Completely Different: In the postgame, the player is able to control anyone on their team.
This made the move Attract into a very powerful move as Everyone Is Bi.
Ambiguous Gender: Unlike in future games, Pokémon's genders aren't shown when you fight them and most NPCs aren't referred to by gendered pronouns (others either use their name or occasionally use "it" or "they"/"them" instead).
Advanced Ancient Acropolis: The Aged Chamber and Ancient Relic friend zones seem to be located in the stone ruins of some advanced civilization - with fountains, detailed carvings on the walls, and even glowing sigils.
Aborted Arc: After the Metapod rescue mission, Team Meanies' world domination plot isn't mentioned again.
Once you have an HM, you can enter the HM-specific dungeon either by keeping it in your item bag (only takes up a single space, but can be lost if you faint) or by teaching its move to a Pokémon and taking it to the dungeon (prevents it from being lost, but may require you to take a specific team member in or erase a good move for the HM move).
Ability Required to Proceed: A few dungeons in the postgame can only be accessed via Hidden Machines, which in this game are rare items found on specific floors of dungeons.
100% Completion: The game acknowledges recruiting all Pokémon in its Adventure Log.