This is the page for in-game event Pokémon. In other words, those are Pokémon that appear in the games only at a particular time, or only once. Essentially, these are either egg, legendary, slot machine, or given Pokémon. An example would be Latios in Pokémon Ruby. An event Pokémon would be Latios in Pokémon Sapphire, since it requires the use of the Eon Ticket. Add as you like. Please be accurate, and only add what is needed. Natures and genders vary, so don't put it on unless it's 100% (gender only).
All the non-event Legendary Pokémon go here.
All eggs given by NPCs go here.
Slot machine rewards go here.
Also given by NPCs, not in egg-form...
None of the above.