Boss HP recruit glitch
In Pokémon Mystery Dungeon: Red Rescue Team and Blue Rescue Team, if a boss Pokémon uses a Reviver Seed and is recruited in the same battle, it will have the same maximum HP as it did when it was fought as a boss encounter. For example, Deoxys will have 950 HP and Rayquaza will have 600 HP. This amount will continue to increase if the Pokémon is leveled up or if the player uses a Sitrus Berry on it.
While traditional gameplay discourages from doing so, there is nothing that prevents the player from placing a Reviver Seed on the ground and then walking away from another Pokémon to cause them to pick it up. Thus, no setup is necessary aside from a Reviver Seed in the bag and potentially a Friend Bow to ensure the target Pokémon is recruited upon defeat.