From Bulbapedia, the community-driven Pokémon encyclopedia.
This is a list of non-player character's Pokémon's determinant values (DVs) in Generation II; the DVs are also known as individual values (IVs). In this generation, all Pokémon owned by the same NPC share the same DVs (Attack, Defense, Speed, and Special).
For comparison, in Generation I all NPC's Pokémon shared the same DVs: 9 for Attack and 8 for Defense, Special, and Speed; these values are re-used for several Generation II Trainers.
In Generation II only, the shared DV glitch is activated if the NPC's Pokémon uses Transform twice and the player forces the NPC to switch Pokémon with Roar or Whirlwind, which causes the next Pokémon sent by the NPC to share the DVs copied from the player's Pokémon. This can be used to turn the next Pokémon sent by the NPC into a Shiny Pokémon.